If its to that point best to speak to your psychiatrist as its a potential side effect of Lamictal and they could see what the appropriate follow up is. Also see if it varies during the day (such as when you first take it) or if the headaches remain the same and/or at the same intensity all day and let them know the specifics of that as well.
I have seen on other boards that some people have had success with drinking extra fluids and adding in some gatorade. Not sure if it works, haven't had that side effect.
I have been on Lamictal for 10 years and take 400 mg a day. 200 in am and 200 in pm. I really notice if I don't take it. It has worked great for me. If I am hyper it calms me down. A friend of mine can't take it. So, everyone is different. If you feel worse with it than without it talk with your Doc. There are other mood stabilizers out there that may work better for YOU.