In love with straight best friend.

I've known him for about a year now and I've been crushing on him since we met. When we're together, I'm happy and nothing can change that. Being friends with him and hanging out with him is one of the best feelings in the world. But other times, it's hard.I get jealous very easily. He's interested in a girl right now. A lot of people think he may be gay/bi, but I've known him for a year and I know him a lot better than most people, and I'm pretty sure he's straight. Whenever I see them together, I get angry and sad and confused.So I suppose I'm asking what exactly I should do in this situation. I want to be his friend, I love hanging out with him, and I would be fine with being just friends, I just want to lose my feelings for him but it seems impossible. I'm still in the closet and I have a feeling if I told him I was gay, or how I felt, he wouldn't be able to be friends with me anymore, and I obviously don't want that.tl;dr: In love with best friend who's straight, I'm still in closet, feel if i told him friendship would be damaged. Do I break off friendship? Do I tell him?