In reply to Pyreneenemec:
My sister has very similar problems a few years ago, not caused by a specific incident but it turned out to be a combination of lower back issues and eye sight problems that resulted in intense headaches that had her laid up in bed for days on end with the curtains drawn (bright light made the headaches worse).
She saw numerous doctors who had no idea, thought she was imagining it and implied she was being a bit of a wuss! In the end she got back exercises from one doctor and new glassescontacts from the opticians and the problem went over time.
I have no idea if this is in any way relevant to your case but don't let doctors put you off having it looked into, if you perservere they will figure it out eventually.
Hope you recover soon.
Chris