Siatic nerve pain!

Today I've suddenly developed terrible siatic nerve pain. All day it's been annoying at work but now that I've sat and relaxed it hurts to move like at all. I read somewhere online that it could be caused by a tilted uterus (which my Dr said I have) and it supposedly lasts until around 15 weeks when the baby moves forward. Im just wondering if anyone else it dealing with this or knows any other information about what causes it this early (9 weeks)