My friend, things that OTHER people do is NOT your fault! If someone cannot follow directions, then too bad for them!!

But it's NOT your fault! And if you get a B for a grade, that's GREAT! It shows you tried VERY hard, and a B is an excellent grade -- how could you be a disappointment to ANYONE??? Dont your parents give you kudos for that? If not, they should! I ALWAYS showed my kids that I was proud of them if they got a B on their report card or on tests, etc.
As for the feelings you've been having, you SHOULD talk to your counselor at school. They keep things private, unless they think things are serious enough that you're a danger to yourself or to others. If they think that you're in imminent danger to yourself, they MIGHT call your parents and talk to them. But anyone else, they wouldn't talk to. So PLEASE talk to your counselor, ok? You really do need someone to talk to -- to unload some of these feelings on, and to get some advice. Ok? God bless and you can message me any time if you'd like to. Big hugs, Lee