I think, in my humble frustrated opinion, that it has something to do with the rise and fall of hormones..... and I don't see why they haven't come up
with that yet. I do know it's uncomfortable, and tonight, it's driving me crazy.
The only thing they did for me, was give me a mild tranquilizer, which did seem to help, but I hate taking anything like that, so I try to breathe in a paper bag..... it's just so frustrating, that the docs tell us it's in our head! It's NOT.