should i or should i not?

If you like him a lot and you know for sure that he has feelings for you, I say go ahead and tell him how you feel. He will never know how you feel about him unless you tell him. If he does like you, it is impossible for him not to treat you differently after you tell him and who knows, maybe he will realize that you are the better one for him and not the girl he's with right now.

I think you are struggling right now because he has a gf and you dont want to be the one to break them up, I understand but sometimes when it comes to love you just have to be a little bit selfish and think of yourself first. Just because you dont get in the middle of this doesn't mean they wont break up in the future, if you have a chance to tell him now, dont hesitate and just tell him.

~I was in your situation where the guy had a gf but we both liked each other, well I ended up telling him and we're dating right now but I did not break them up because it was that girl who dumped my bf and thats why I'm dating him now. I just wanted to say this so that ppl wouldnt think I'm telling you to break them up just because something similar happened to me.

Well, who the hell cares about his gf... i dun think it is true that he really has a gf by the way...= =... Just tell him, if he loves you, he'll be with u
if he doesnt, oh well, get over him then... since there's nothing else you can do.

well ; as you can tell , he has a girlfriend.
you gotta ask yourself if you really want to "break them up"~
because once you tell that guy && if that guy likes you too, and if he say that he's going to break up with his girlfriend, she's gonna be hurt.
think deeply before acting[: