Hi, and welcome! I'm glad you found us and joined in. What medications are you taking? Perhaps some of them are interacting and causing some of your problems. The "seizing" you mentioned could possibly be caused by medication or perhaps epilepsy. I'm not a doctor but I sure would ask the doctor next time they see you and see if these could be possible things to look into. There are quite a few on this forum that have had difficulty with some of the medications they are passing out for fibro. I personally think too much is being used...especially on young adults like you. This is my humble opinion.
I use ibuprofen with food, extra strength Tylenol, malic acid/magnesium supplements and vitamin D3 supplements to help with pain and fatigue. In Fibro 101...the first thread on the forum that Karen mentioned, has links to good information about fibromyalgia and two of the links are about these vitamins and nutrients and how they work in your body. I know they have helped me and others but they don't help everyone. My doctor said they wouldn't hurt me so I tried them and got some relief.
I'm so sorry for the traumas you have suffered. It is hard being a teen...even when you are perfectly healthy. You need to search for friends that are more like you. I had two special friends in high school. I suppose we were considered "dorky" because we didn't do the partying, either. When I got in college, I was one of the few that never tried drugs. I remember going to a party and everyone started sitting on the floor in a circle with their legs crossed "Indian style". I was so naive that I thought we were going to tell ghost stories! 
Nope. They were passing around a popular drug and I had my date take me home. So, I really didn't fit in with the culture of the time either. But you know what? I believe this made me stronger, more independent, and able to handle life far better than those that followed the popular crowd. You sound very mature, too. You know what you want out of life and I do think you will achieve it! If you want it badly enough, you can do it.
Now about classes. I would go to your counselor and let them know about your having fibromyalgia and see what they can do to help you with classes. Fibro is a disability. That's why you are having the problems you are having right now. Perhaps this will all change if medications are causing some of it but in the meantime find out what you need to do and what help you can receive. Teachers will be more understanding and lenient if they know what you are going through...at least most of them would be. You probably need a note from your doctor but there IS help out there for you. Check it out and let us know what you find out. Okay?
Keep those wonderful dreams going. I've had fibro for 23 years and have done a lot of traveling. I've been to Italy, Austria, Switzerland, and Germany. I've stood on glaciers in an ice field in the Canadian Rockies, laid on the beaches in Hawaii, Jamaica, etc. I've snorkled and even parasailed with fibro. It can be done. You are young and have your whole life ahead of you and it can be a great life, too! I know because I've had a great life so far. It isn't how I thought it would be but I have been able to figure out how to work around fibro to do the things I want to do. That's where this forum comes in handy. We share our ideas and help one another. So, you have come to a good place. We have wonderful members that love to help one another and, as a bonus, we really do care about each other, too.
I'm looking forward to getting to know you. Don't hesitate to ask questions because we are here to help you. I hope to hear more from you soon.
Sherrine