Well, I recently started on lamotrigine (about four weeks ago) and I had a little bit of diarrhoea here and there, which I just didn't think about until I read your post. Mine didn't last very long, though. I guess it is just my body getting used to it. You're titrating the lamotrigine up slowly to lessen the chance of Steven-Johnson's syndrome, right? I suggest you wait a month after you finish titrating up and if it's still terrible, try something else.