Have suffered them all my life. Always got them during pill free week so obviously hormonal. At that time (about 15 years ago) I was advised to continue taking pill so I didn't have any hormone fluctuations. This worked though nowadays would not be advocated because of increased stroke risk.
Since having kids and suffering still for the last 3 years I've been on the mini pill. Not for contraception as DH had the snip but to balance out hormones so I don't get the migraines (or periods). This has worked pretty well and have only had two during this time that I can think of however one has slipped under the radar and I'd forgotten how sickening it is.
Same thing, always on left side and once there will last for exactly four days. Feels like someone has poured hot molten lead down one side and are then trying to pull it out through my eyeball. Teeth like a tuning fork has been twanged on them and a general feeling of nausea and shut down.
So, once it's there, absolutely nothing shifts it. Any fellow suffererers have a miracle cure I'm unaware of?