I have been on Seroquel since July,2007. I gained at least 20lbs ...

I haven't noticed weight gain with Seroquel but I gained 20-30 pounds on Remeron and so did two other people I know. I stopped taking the Remeron a couple of years ago and my weight went back to normal within a few months. Could it be the Remeron?

Remeron has been referred to as "pot in a pill". It causes strong cravings for sweets and carbs, causing rapid weight gain. That could be your reason for the weight gain. I'm surprised your doctor would prescribe both Remeron and Seroquel together, as both cause drowsiness and dizziness.