Sorry to hear your getting migraines on top of your ibs. No fun at all I'm sure. 3 - 6 hour migraine episodes are quite common. Mine can last anywhere from 15 minutes to all day long for several weeks. Besides pain and discomfort suck even if its for fleeting moments.
First off I would go and see your doctor. The feeling of falling could be unrelated and something as simple as an inner ear infection. I've had vertigo twice and it lasted on and off for a week at a time. It ended up being an inner ear imbalance just before i came down with a cold.
They eyes thing could be part of your migraine aura, but again i would really consider going to see your doc about that. My migraines often affect my vision but I also have double vision. So i'm not sure if that already makes me hyper sensitive to these things.
If your doctor is not aware of your migraines you should tell them.
Anyway, i'm rambling. I really hope you get some good feedback...and go see your doc. Take care and good luck to you.