Can't blame you. I don't know a whole lot about seroquel, other than it making you tired. When it comes to the melatonin, I would take it at night and not actually sleep for a good four hours after. When I did sleep I'd sleep alright but I'd wake up feeling hung over. It works different with everyone.
Does anything else work to help with the drowsiness you deal with during the day? I use to have my Effexor in the morning because it woke me up a bit; I was kind of on an antidepressant/anti-anxiety cocktail for a while. I don't know if you're taking any medication that has that sort of side-effect or not. If not, keep at it with the caffeine. I don't know much else that will wake you other than getting a low dose Adderall prescription.