I Have Been Taking Amitriptyline For Migraines For 3 Months

I have been taking amitriptyline for migraines for 3 months -- however, I have gained weight (I eat healthy and exercise daily) and my migraines are coming more frequently then a month ago. My doctor has prescribed topamax for me and wants me to take both the topamax and amitriptyline together for a week. I have read it is not good to take both meds together because it can cause extreme dizziness and feeling tired. Is it necessary to take them both? I need to work and cannot be drowsy. Can I just start the topamax by itself?