Really really scary situation?

I have been with my boyfriend for two years, I've broken up with him about 3 times before, and I think the reason I came back was because I was scared of the changes, well now, I think I should go for good, we're not bonding right anymore and he's rude a lot of the time. SOME name calling gets irritating. I know I just need to get a backbone and do it, and suck it up when all the emotions come rushing in after. Here's the big big problem, His friend and I admitted our feelings for each other. we waited two years to, and we did. I'm still with my boyfriend, but I dont know what to do, I think its up to his friend if he wants something with me, of course we would wait a loooonnng time before we got together, but we already kissed. So yeah, in a way, I cheated. Advice please. please please