Possible subarachnoid hemorrhage?

Hello,

About two weeks ago (November 16th, 2009 to be exact) my boyfriend experienced a severe headache (he later explained that it felt like someone hit the back of his head with a hummer). The pain lasted about five minutes and subsided. Later that day he told me that he still had headache but not as bad as the earlier one. He experienced the same type (the hummer type) only twice after that (Nov. 18th and 19th) but he's been having the constant headache sine the first headache and it seems that it is getting worse every day. In the early last week he went to see his doctor and he run CT scan for him but the result came negative. He got his MRI/MRA done recently and again the result came back normal.

By doing on line researches, I suspect that his first severe headache may have been caused by a subarachnoid hemorrhage and the doctor is probably looking for aneurism. My first question is...is it ok for the doctor taking so much time to find out what caused the headache? According to the articles that I read about SAH, it is critical to get the right treatment as soon as possible after it happens. It's been over two weeks now since he experienced the first headache. I am so scared if he will get another SAH anytime soon (if that's what he had a the first place).

My other questions are...
1) Given he had SAH on the Nov. 16th, what is the possibility that he will experience another SAH without getting a treatment?
2) If he didn't have SAH, then what would be the possibilities causing such a bad headache?
3) How accurate MRI/MRA to find aneurism? (His MRI/MRA result was normal)
4) I have read that MRA is not good at finding if a subarachnoid hemorrhage had happened or not...is it true?


Thank you,
N