Sounds to me like you're possibly polyamorous, and trying to fit into a monogamous mold. Which is really frustrating. I've been there. Did it for 14 years. Also sounds like your friends are pressuring you in an unfair manner. You should really just have it out with them in a very frank (but non-screamy) way.

It's really all up to you, ultimately. If you're crazy in love with this guy and he's the only person you want, then fine. Do that. And if you simply can't live without this triangle, then do that. But don't sit on the fence. You aren't doing anybody any favours by lying to them. Especially you.

And, just so you know.. It's okay to be this way. I'm finding out that A LOT of people are. Just be you.