We respond to some sleeping meds/antidepressants differently. Perhaps you're just not reacting well to the Seroquel. Many of these meds cause weird dreams/nightmares. You might ask your doctor about this and see what he says.
Something that helps me sleep are the CD's of nature sounds -- there is a whole packet of them, with sounds of the ocean, rain forest, birds, rain, thunder, etc. They are wonderful and they put me to sleep almost immediately -- and I have a HORRIBLE time getting to sleep as a rule. I'm so glad I have these CD's. You can buy them any place that sells CD's.
I hope you can finally get some rest. Best of luck and God bless. Hugs, Lee