Oh Lordy YES these meds can affect your digestive tract! I have IBS so these AEDs have wreaked havoc on my poor tummy...so much so that my doc ordered a colonoscopy/endoscopy (bleck.) Thankfully, no polyps (there is a history of colon cancer in my family) but I have developed an ulcer due to the meds.
Hopefully your stomach will adjust to the meds in time. Mine is just hyper-sensitive, I guess. But hey! I've lost 28 lbs I didn't really need to drop since I started riding the medication train 3 yrs. ago (which has included stops in Lamictal-land, Dialantin-ville, Topamax-town, Carbatrol-city, um, what else? Oh yeah, Lyrica-land was especially fun, now I'm staying in Keppra-ville and the Zonegran-Zone!)
Hang in there.