hmmm ... very tough situation ...
First, i think you should talk to your mom... tell her that you tried your best and you some support of from my family, not bulls**t from her... and that her comments about you being worthless and that you are a waste of time are really hurting you... [not to be rude, but i think your mom needs to understand that not everyone is perfect and gets 101% on everything... if she thinks that ur a waste of time, i`m sorry but its NOT
YOUR problem, and SHE was the one that decided on having a baby and she should accept the fact that you can't expect your children are gonna grow up to beocme BILLIONAIRES or the smartest person]
anyway. you should just try your hardest ... ALWAYS pay attention in class and preferbably take lots of notes ... !
good luck with everything !