I need help..... I am dying to tell my best friend how I feel about him, but I don't know if he's gay or not. Advice?

So, ever since i can remember wanting a relationship, I have wanted to be with one of my childhood friends (since the 3rd grade). We fell out of touch around the start of high school; part because we went to different ones and part because I became quite depressed for a number of reasons.Now, I'm going into my last year of high school and I'm beginning to get head straight and my life back together. I recently got back into contact with him and we've been talking like we used to. I just.... can't bring myself to tell him how I've felt. I don't even know if I should. When we were younger, he kinda gave the impression that he was into me, but he also had (not sure if he still does) a girlfriend.I have more to say, but this has gone on long enough... if you can give me some advice, I'd appreciate it.... I'll probably put some more details in the comments....