I can't focus. it's really messing my grades up and it's been like this for a while but now it's really messing up how i live. what could this be and how do i focus in class?

If you want to focus you have to find out the distractions and you have to override or get rid of them and at the same time you should concentrate on the factors which help your focus. E.g. you need to be in a silent room when study or some people will study better when listening their favorite music, etc.

Do you mean your eyes dont focus or your brain does not focus. Asky your parents to take you to an eye Dr or a family Dr. for evaluatinon. Meds work well

Your problem of focusing is a a matter of self esteem and confidence. You may need counseling to help you achieve your insecurity.