I Have Had Hives For About 7 Months. I Have

I have had hives for about 7 months. I have been on steroids but decided to stop taking them, they DO NOT agree with me at all. I've had EVERY test that every doctor could get, spending well over 6000.00. Everything says I'm fine. Now it seems I'm only getting them when I'm close to my period. Is there any explanation for this? Does anybody have any suggestions? I'm extremely frustrated. Thanks for any advice