Was I Unfair To My Ex?

am posting this as I'd like to hear some impartial opinions so that I can learn from it and not make the same mistake in the future.So basically:I meet this guy and things go so well, I stay the night and we start dating from the very first day. We connected like we've both not connected with anyone in forever. Within a week we are spending almost every single day together.Within a month I am at his house every single day. Even when he isn't there or at university I go to do my own work etc and even have my own food there and everything.We talk feelings and tell each other how much we like and care about each other. We both haven't felt like this for anybody in years. We decide to keep the relationship 'open' to sex with other guys but no dating. Just since it had only been a month at this point and didn't want to add any pressure to the relationship yet.That being said, none of us meet any other guys or anything. We spend all of our time together and have no interest in anybody else.2.5 months in, I ask him for a couple of weeks to myself as I am going through some personal stuff and need to get my head together. He tells me it feels like a permanent break away and then tries to save face by saying he was going to ask to take a step back anyways.A couple of weeks later, we meet again. Things are a little awkward and not as lovey dovey. However next time we go to the cinema and hold hands etc, he tells me it made him really happy and he missed it.The next few weeks are kind of back and forth awkward. There seems to be some tension between us for whatever reason and I was getting frustrated as one minute he's hot the next he is cold. It was emotionally very stressful for me.Eventually I lash out a little and kind of just say "what even are we right now?" he takes offence to that and ignores me for a day then we hang out the next like nothing happened.A few days later he tells me he just wants to be really really good friends as he doesn't have the same feelings for me anymore.I decide to go home to my home country and spend some time with my family. I took that as us breaking up and wasn't really prepared to just be friends yet.We spend the last couple of days together. They are magical and just like old times. We make out, cuddle, sleep together intertwined etc. and I write him a goodbye letter which I give the next day. I go home to pack before going back.I go to meet him and he is in absolute dire state with tears, hugging me etc. and he gives me a letter of his own. Telling me the past month due to some weird conflict between us he didn't feel like the future we pictured together could happen, but the last two days made him feel like it would be possible after all. Just as I was leaving.He tells me he needs me in his life, loves me, cares about me so so much, can never replace me etc.We kiss and say our goodbyes at the train station. He is distraught.I tell him on the plane on the way home that I will be back in a few months. He tells me he will wait for me cause no one could replace me and he only cares about me but can't promise he won't do anything with one of his friends one night while drunk or something but "even that probably won't happen and that's the most that will happen" aka no dates or anything.I am like, fine, I don't care about that.He makes a google album to share our life together and we talk everyday etc, share everything of our life and I am really excited to go back.Then my own friend messages me with screenshots of him asking for **** pics, saying "my name told me it's big ;)" and his grindr bio was "looking for horny twink". This was a week after me leaving. I was mortified. But I didn't find out until three weeks later so called him out for it then.I call him out for it and he assures me it doesn't mean anything, he only cares about me etc. initially he was just like "what? drop it" but then he elaborated on that points. It concerns me and honestly I act out of emotion as I didn't want to lose him and there was nothing I could do while halfway across the world from him.. I cared for him a lot and mostly I worried about him replacing me while away, not so much just asking for **** pics or whatever.Then he tells me I am being dramatic and ignores me for like an entire day. We start talking again kind of like normal but I am feeling somewhat insecure in us now especially as he asked a couple of times "when are you coming back? and "I can't promise if you aren't back by April / May I won't go on dates with either guys" which worried me even more as it led me to think he was getting tempted. Like dude we have so much plans together and you can't wait a couple of months?Anyway I start to panic kind of and start asking him to assure me he will actually wait etc. I told him idc if you have sex with one of your friends but I can't be there to share the things we normally do like cuddling, kissing, going on dates and spending our time together etc. so if he done that with other people I'd have a problem with it.He tells me he will wait.The next day he tells me he is meeting a guy for coffee. I ask him what his intentions were and he says friends and I am looking into it too much. Then he tells me that I am halfway across the world and he will not be limiting himself if he wants to pursue something. Right after saying he wants to be with me "so so so bad".Then the next day I ask how it went and if anything happened.. he snaps and tells me he doesn't want me back "right now" and that I was being a nag and putting a ton of pressure on him.This all occurred over a period of like five days. I have never acted like that before and don't believe my concerns were entirely unjustified..Then he starts not talking to me, eventually starts feeding me breadcrumbs and when I ask if he's being distant, he says yes and he can't imagine a future with me anymore cause it feels like a prison sentence.What strikes me is that it was right after meeting another guy. It kind of shattered me a bit as I have never given so much of myself to somebody and it seemed like a few days of me acting a bit out of character had completely abolished the four months we had spent together with nothing but positivity.Now I am 99% sure that he is dating another guy just two weeks after this (heard from my friends) and it feels kind of sucky that he's replaced me so easily after everything between us. But mostly I feel bad cause I acted needy for a few days and if I didn't do that things may be different.Idk. I am hoping to learn from this and ask your opinions on the situation as it's really difficult for me to comprehend. I feel like a fool for getting needy but at the same time idk how anyone could not start to worry after seeing those things and I acted out of panic I guess.He also sold some of the stuff I left at his house and blocked me on social media when he realised I was still coming back (he isn't the only reason I was there) cause he "didn't know how to handle it" and "doesn't think it's in my best interest to come back"... he emailed me this.Everything just seemed so out of nowhere.