Why do I feel this toward a gay friend?

This is going to be long. So please bear with me. Besides that, this is my first reddit post. If I said something wrong, please correct me.I am gay, tested HIV positive since July 2017. After I achieved undetectable viral load in January, I mentioned it on my Grindr profile. Then, came a guy. He contacted me on Grindr, started by asking questions about HIV, then it slowly turned into a friendly chat. That day, we exchanged pictures. Then few days later, he contacted me again, we eventually exchanged numbers. Initially our conversations through texts messages were limited. After a few weeks, we decided to meet up.Meeting up with him changed everything. I slowly grew fond of him. We have met up for four times before today. The more we met up, the more I got interested in him. I viewed him more of a friend than something romantic. One of the reasons I tried to limit my relationship with him because I doubted that I was attractive or interesting to him.Today, he sought help from me. All in all, I knew he had sex with a man the day before. Now, I knew that he had a bf before and has a girlfriend right now. However, right now, after seeing him and spend the morning with him with something, I feel weird. I feel down. I feel uneasy. Probably, it has to do with the fact that he had sex with a man? But, what confuses me is, I never consider him as my love interest. I would never want to have sex with him. So, why would I feel sad knowing that he had sex with a man, while I myself have been hooking up with men too?I hope anyone who has experienced such feelings before could help me out. If not, probably you can share some tips to get over such feelings. Thank you very much.