How am I so bad at school?

I have always struggled with school and I honestly don't understand why. I am 22 now, and I watch some of my friends get their degree, or go into medical school and I feel so jealous of them. I wish I was that smart, but my dumb ass can't even get a degree. And I know I should stop making excuses, but I also have a full time job, and sometimes I just don't feel like going home and studying, but I know I need to. And I know I need to do better. Any tips on how to get better at school? And am I the only one who is this bad at school?