Could be your body adjusting to both, apparently your metobolism slows once you've quit smoking and if you've been smoking a long time, it's gonna take a while to adjust - just persevere. I commend you for doing both at the same time, I tried quitting smoking but it's didn't happen (I guess I didn't want it enough really) - I'm not a huge smoker, maybe 5 - 10 per day, but have been smoking 25+ years.

Vikki