I'm sorry I don't have anything to offer with regard to your headaches. But I noticed no one else had yet replied to your post. So I thought I would. I know you mentioned having had CT scans & MRI's of the brain. Have you ever had yourself checked out neurologically for such things as the possibility of damage to your cervical spine? I would guess a blow to the back of the head could do some damage there as well.

You mentioned struggling with suicidal thoughts. Here's a link to an article, from Psych Central's archives, that offers suggestions for surviving suicidal thoughts:

How to Survive Suicidal Thoughts

My best wishes to you...