There is no way you’re going to get the best grade you can on the upcoming exam until you figure out how to manage your stress.  I am serious.  You will get to class and your mind will go blank from too much worry.  I know just the thing to calm your nerves.  You have to work a nut out.  I know about these things.  I’ve been where you are and just because I’m a woman doesn’t mean having an orgasm for stress reduction doesn't help us to.  Tell you what, I’m sympathetic to your situation.  I know you don’t have a girlfriend at the moment so I’ll assist you in getting a good nut out.  I’m not going to fuck you.  I will talk you through masturbation until you cum like a good step mom should.