Having dizzy spells every three hours

[Vanoliz]

By way of background I have chronic daily headaches as well as migraines with aura, and have had those since I was 14 (I’m 32 now). I take rizatriptan for the migraines and Tylenol and ibuprofen for the daily headache. Early yesterday morning I started having spells where my mind would start racing with what felt like old memories or de ja vue (I don’t remember what any of these thoughts were actually about) then I get extremely dizzy and nauseated, to where I can’t think or stand, I don’t know where I am and cannot speak. This has been happening like clockwork every three hours. My husband took me to the er last night thinking I was having seizures. They did blood work and a CT (both normal) and sent me home. Any idea what is going on? Is it serious? As a side note I started birth control about a week and a half ago, as they’re doing a procedure to remove a polyp from my uterus and wanted to postpone ovulation. No idea if that could be connected. ER doc didn’t think so.