Okay, I moved ahead and the problem is settled for now.

I see my non school affiliated therapist on Friday. I wish it were sooner, but I'm afraid to go to a school therapist, because it'll just make things worse if I have on record that I'm complaining about a professor and trying to duck out of my responsibilities.

The main reason I want to go is that I want to explain that I wasn't slacking off on purpose -- I misunderstood what I was supposed to do. It is my fault I misunderstood, but I'm irrationally mad at my advisor for not explaining things more clearly and I know my anger is inappropriate. If I go to anyone at school and try to explain what the problem was, I'll only look ridiculously whiny and entitled, and everyone will take his side over mine (as they rightly should.)

I just have to learn to live with the fact that it was my fault and that I have no right to ask for help after I screwed up. If I'm not willing to learn how to behave appropriately, then I don't deserve any special consideration. I just want to crawl away and pretend that I'm not this awful person who creates these horrible problems for everyone else.