Messed Up and Stuck

VERY LONG STORY IM SORRY BUT I NEED HELP~
I'm 19, and my boyfriend just turned 20, I've been in a long distance relationship with him for 9 months now. We communicate less and less, and I've began to lose interest, especially with him not doing anything productive with his life. Less than a month ago I met a new friend who I could produce music with and actually feel like I have a chance to get fame with. We're just friends, but a couple weeks ago after recording we ended up snuggling and fondling. I don't know how I didnt see that coming, but when it happened I couldnt help it. I don't know if it was the fact that was bored that made it so easy or what. I never planned to do it again, and me and my new music partner have no affection for each other whatsoever and never spoke of what we did. As it ate me alive, I did research and based on my circumstances, most of it boiled down to saying I shouldn't tell him. So instead, I told my guy that we're drifting apart and I'm getting bored. But then he broke down in tears and told me how much he loved me and wanted to do anything to make it right. Of course, me seeing a guy cry over me made me cry and feel extra guilty about what I did and I told him what happened.
He wasn't mad at me, but he wants me to never speak to this new music partner again. Despite the small random fling, we became best friends in less than a month and I don't want to give up on all that hard work we put into music, the gas money, the potential fan buildup, everything. And its rare when I get a best friend in real life, I could relate to this guy better than my friend who I knew for a year and a half. I don't want it to go to waste. I finally got out and began to live life .
But I do love my boyfriend, but I don't want to stop talking to my new friend just to sit here and try to make things work while I watch my boyfriend go through another semester without school or work, or doing anything somewhat impressive. I also don't want to watch 9 months go down the drain. WHAT DO I DO?!