I've been on seroquel for nearly 18 months now, and if you would like to know of my expereinces with this medication please feel free to pm me.
With regards to your metabolism, if you do CD (and any other deit) your metabolism will decrease a little as you take in less calories, but with CD you lose weight via ketosis and fat burning, so i'm not sure how that will work out for you.
What i would advise is that you see your GP to discuss the diet and possibly ask for a blood test for your thyroid to check if its functioning ok.
Sorry i can't be more helpful with CD, but i do know this medication inside out with having researched it for side effects and my experiences and having seen 3 Pdocs about it (especially where weight gain is concerned), so if you want to discuss anything about it feel free to pm me.
All the best.
M_B xxx