Help

I (16f) have this friend (16m) and we are really close. We became friends when he first started dating his girlfriend (17f), and I was in a relationship too (not anymore.) Since then, we have become closer and closer, and I think I’m finally falling for him. They are very committed to each other, however, he tells me that he would love to have sx with me if he didn’t have a girlfriend. At least twice a week he asks me if I would get with him if he was single. I am friends with his girlfriend, but not close enough for me to tell her about it, as I am more loyal to him due to our friendship. This is because we have helped each other through the darkest times, and I can honestly say i would take a 🔫 for him without a second thought. I am currently exploring a new potential love interest (16m), and when I mentioned this to him he changed, and became cold and jealous, which I have never seen from him before. In a lesson the three of us were in today, he gave him dirty looks and was ignoring him on purpose, making it obvious something was wrong. When I asked him about it, he told me it was nothing and to leave him alone. Again, very out of character for him as he is never like this with me. I would understand his jealousy but he is in a relationship of his own and has no authority over my love life. I just don’t know what to do honestly.