I fell in love with my best friend but I have a boyfriend and I haven't been happy with him for a while

I fell in love with my best friend. Wow another cliché. We like each other. And that's new for him because he's never liked anyone. He tried to never like someone so he built a lot of walls up and our friends say it was a miricle I got him to put down a wall for me. Keep in mind they've been friends with him longer than me and him have been best friends. Anyways my dilema is, my boyfriend is not graduating today because he failed a class by 2 points. He's a very bright young man though. But I haven't been happy since like 7-8 months ago. That's when I found out he cheated. Now I know some of you are like "you should have left him then." Which is true, I should have. Anyways, my bf and I have been together for a year and almost 9 Months. I don't know what to do. I talked to my mom she said I'm inconsiderate. And I see why she said that. I just need help. Please someone help me.