Hiya,
PTSD is an option but you can have flashbacks of memories with depression, bi-polar disorder etc... as well. I still have flashbacks of negative memories (much less than I used to though) and I know that it is hard to put them out of your mind. It sounds like you are under a lot of pressure as well and that will only make things worse. (I know because mine are worse in Jan and May... when the exams are lurking around!). For me, relaxation is the key. I use mellow music and meditation. Its hard to start ith but once you get the hang of it, I find it works really well. As for Serequol, my sister has taken it and it seems to make her dopey so I guess it should make you go to sleep but meds affect people different ways.
Darren