Missing Periods, Heat Flashes In Face Causing Hives, Lower Backpain, Migraines. Suggestions?

Hoping someone might be able to answer my question. I have been to tons of doctors with no resolution. Back in August I start have the main symptoms....missing cycles or very light spotting only, major heat flashes to the face and recently these hot flashes have turned into hives on my face, neck and upper shoulders. They always occur 2-5 days before my cycle should start but I typically end up only spotting for about 3-7 days then it goes away. I am now alos having lower back pain as well. It feels as if something is stabbing me in my tailbone. It doesnt necessarily feel like muscle strain but just a pain and its the 2nd month its occured at the same time I should start my cycle. The hives are so uncomfortable and I would really like to figure out whats going on. Also, prior to all of this I have very heavy cycles, broke out with psoriasus (sp?), a few years ago and suffer from heart palpitations that I take medication for and migraines espcially a day or so before my cycle. Not sure if all are related but through I would mention them.