Migraines getting worse...

I'm 19 years old and was hit by a car almost exactly two years ago. Shortly after the accident, I began having migraines (I'd never had one before this, but the first time I had one I knew it was a migraine). They were always accompanied by nausea; dizziness; sensitivity to light, sound, and smells. They were completely incapacitating but after taking a nap, it would be gone. I was getting them one to two times a month. I was put on a medication (Sumatriptan) to take at the onset of a migraine and it was working very well.
About 6 months ago the frequency increased to about once a week.
Then again, about two months ago, it got severely worse. I've been getting them at least twice a week, sometimes more. I saw a doctor and my medication was switched to a daily preventative medication (Nortriptyline). The medication is not working at all. Along with the increased frequency, my migraines have increased in severity. Any light at all and any noise above a whisper makes my head feel like it's exploding. The pain makes it hard for me to walk at all. I get so agitated, I don't want anyone touching me. It's gotten to the point where it's hard to even fall asleep because of the pain. I've noticed that the new migraines are always on the right side of my head, if I don't keep my eyes directly ahead it's 10 times worse, and if I apply some pressure to my right eye, it feels better...

Does anyone have any idea as to why they have gotten so much worse? I have no idea how to handle them anymore, I feel like I'm completely losing half of my week to these migraines.

Thank you!