medication allergies...do they ever go away?

I am currently on Depakote and Keppra, and my Dr. is trying to get me off of Depakote due to severe weight gain. I just tried lamictal and I got a rash and itchiness from that---so they took me off of it. Now that I have upped my Keppra dosage my itchiness has returned, although no rash. Are these allergies? I am of course informing my Dr. of this, but I REALLY do not want to go off the Keppra. It works great! The Depakote works a little less well and the weight gain is really a problem. I am now considered obese and I have to keep buying new closes, so I don't know what to do. I have already tried Tegratol, Lamictal, Topamax. Will there be anything else to try.? Everything I have tried has controlled my seizures, but everything seems to have either a side effects or an allergic reaction. Is this going to keep happening? I have told my Dr. that when these effects happen I am willing to stay on the drugs to "wait it out" but they don't want to do that. I am sure they are being on the "safe side" by doing that. I will be itchy every day, I don't mind. Also do you think that the Depakote and Keppra together could cause the itching? Any thoughts or ideas would help. I am so frustrated and I don't know what is going to happen. ebaum