Hi Sabrina,
I'm not on it anymore, but I took seroquel in the past for sleep and it worked well.
For nightmares, I recently began a blood pressure medication called prazosin. It was recommended to me by a friend who also suffers from nightmares and it works for them. I didn't have high hopes but I have not had a nightmare since starting it 4 days ago. Maybe it's worth trying for yourself. Nightmares are definitely not fun!