How do you ask somebody if they're not interested in being your friend anymore and if so, why?

So I have this friend, who was my ex's housemate and we ended up getting along and would hang out a lot even after my ex and I broke up. A couple of months ago we kinda started drifting apart (which I feel was more on his end). I would hit him up to chill and as where he would normally be free, he started saying he was busy or just wouldn't reply or answer his phone and I wouldn't hear from him unless I had made the effort to contact him.A few weeks ago I invited him to a bon fire on the beach with a few friends and coworkers of mine. We did that a lot last summer and it was really fun. He replied "sounds like fun", but didn't say if he was down to go or not so I asked him if he wanted to go and he never replied.A while before that we were hanging out at his place and had been drinking beer all night so we were kind of drunk and we were just hanging out in his backyard chatting. He started talking about my ex (which unfortunately, is a slightly sore topic), he mentioned to me that my ex had invited him to a 3-some with him and his new boyfriend and he said he had declined. He knows how I feel about my ex, and you would think that he would know that I wouldn't want to hear anything like that. It still bothers me to know that about my ex, but I decided to let it go because he was drunk.There was another time where he would send me text messages and Snapchats that would imply that he was interested in me (which I had ignored). One day he sent me a text, and I can't remember what he said, but I told him that I kind of liked him. I probably shouldn't have. He didn't reply for a while. Eventually he did, and he said he wasn't down with that and said he was just joking. He's never joked with me like that before so how was I to know? I feel like he set me up.I can't figure out if he doesn't want to be my friend and has been trying to push me away or not. I have no idea what's up anymore because I don't even hear from him. What should I do?