The lamictal knocked me out when I first started taking it i.e. if I took it and didn't go to bed I would fall asleep on the couch. I did have some dizziness in the am when I got to my full dose and started to take it am/pm. Both of these side effects have gone away.

As far as drinking water, no I wasn't told to increase, but I normally drink a lot of water and had been on lithium before which I definitely needed to drink more. Dehydration can cause one to feel fatigued.

I can't remember if you went off your mood stabilizer prior to going on the lamictal, but that may be part of the issue. I had and my mood was all over the place until I got up to the full dose.