How To Treat Migraine Despite Taking Imitex?

yes, i suffer with horrible migraines since age 16. Now that i am 43 i still have the same issue. Imitrex is my Saving grace but what else can i take to help prevent? I take Topamax and that doesn t help. I have taken everything to kill the pain but not sure what meds are good to prevent the migraines. I hate meds that make me gain weight, as I am dealing with weight issues now. can you please help me!?