When I was on Topamax I was always tired as well. It never did work for the migraines so I finally got off of it. I tried many other things, so many I can't recall most of them. That was a few years back. I gave up on all the preventive and just take migraine/pain medication to abort the migraine. Sometimes it feels as if nothing is ever going to stop them but at least for awhile I get some relief. There is hope in that at least.
Take care and have a pain free day.