I want to tell her but I don't want to cause problems?

Well basically there's a girl I've become close to in the past few months and during that time I've developed feelings for her. I want to tell her this, but there's a twist, she has a boyfriend, who happens to be one of my best friends, and I've already started a problem between them, unintentionally. This is because she visited my house a while ago and we had a great day, and she told her boyfriend what a great time she had and how nice I was, and he began to feel that she liked me instead, and she told me this, and it was something I just sort of laughed off. Her boyfriend's never said anything to me about it, but he's not the kind of guy to do that. I get along well with this girl, we can talk about pretty much anything and we know we can trust each other, I've helped her with problems before and I know she'd help me if I had any. I compliment her a lot, and she's told me I have nice eyes, which really felt nice. We occasionally say "Love you" to each other (in a friendly way, but when I say it, it feels so much more) and I really wish we could say it with a stronger meaning. But with her boyfriend being one of my best friends I don't want to cause more problems between them, but I don't want to give up on her either, as I do honestly think we'd be good together, and although her current relationship seems good on the outside, they do struggle at times. So basically I'm stuck, shall I tell her I have feelings for her? Or shall I wait for a possible break up despite how hurtful that could be, I don't want to give up again.