Okay, this will probably be one of the hardest posts I've made here, but I'm going to give it a shot anyway, in hopes of helping someone else.
My ex raped me multiple times before I finally (with the help of the friend who is now my husband) left him last year. That's a long story, and I won't go into it now. Suffice it to say that it left me with some serious issues. I've been in therapy for about a year now, and it's helping a lot.
Back to the subject of gyn exams. I've been up in the stirrups since I was raped, and it was scary. I went by myself, which was a big mistake -- definitely take a good friend or a family member you can trust. The doctor I saw was a woman, which I think helped a lot. She was also very professional, and it was all very clinical -- which, of course, is exactly how a good doctor should be.
Is there any reason you have to see the male doctor your mom sees? If you'd be more comfortable with a woman, it would probably be a much better idea for you to seek out a female doctor.
Also, if you call your local domestic violence shelter or support group, they will probably be able to refer you to a doctor who has experience in treating survivors of sexual abuse. That might be a good way to find a sympathetic and understanding doctor.
When you go in for the exam, you may want to let the doctor know that you were sexually assulted. Ask the doctor to be as gentle as possible, and to explain everything she or he does *before* doing it. Better yet, request that they ask your permission before touching you in any way. If it gets too overwhelming, tell them you need to stop.
Breathe deeply during the whole visit, and try to stay as relaxed as possible. If you have a friend or relative with you, ask them to keep you distracted with light chatter when you're not talking to the doctor -- you should know what's going on, but at the same time, you probably don't want to think about it too much, y'know?
If you need to stop the exam at any point, do so. If you need to cry, do so. Don't let anyone bully you into anything you're seriously uncomfortable with.
Another tip -- ask the doc to use the smallest speculum they can, and to warm and lubricate it first. Male doctors are particularly bad about not doing that, in my experience.
I wish you the very best of luck, and I'm very glad you're taking care of your body despite your fears and your past experiences.