Where do you work if you have chronic migraines?

I work at a PetSmart but they're really busy and there's some days I just can't come in because I'm so weak or dizzy that it's just impossible to get there safely. They're very irritated right now since it's the Christmas season and I think I'm getting on their last nerves. I've had a migraine for 4 days now where I'm just super weak and dizzy and I was wondering if you guys have found any companies that are more lenient on this kind of thing, or a way to prevent the dizziness and weakness to where you can work?