If the seroquel is only for sleep, that might be why the doc hasn't increased it.

I remember feeling like I was hit by a truck when I first started lamictal. I felt achy, flu-like, headache, swollen glands even. I was sure I was going to have to stop taking it and was pretty upset about it because I was really counting on lamictal to work. So, I toughed it out and strangely enough, as the dose increased, the side effects decreased. I'd talk to the doctor about it though, but it may just take some time to settle in. Seems like I've heard other people say similar things about starting lamictal.