BIG headache, little answers

I have had headaches and migraines for as long as I can remember. Normally, from stress or lack of caffeine. Last week, after my fun trip to the rheumy for cortisone injections, I thought it was time to ask about my increased head pain. For the past couple weeks, I've been getting sharp stabbing pains in the left side of my head and eye. Nothing brings them on, and nothing helps them. It doesn't last more than a few seconds, but once it starts, I seem to have episodes every few minutes. It was bothersome in the begining, now, I'm scared. I am STILL waiting for insurance to approve an MRI. My thought is, they'll probably approve it next week, and by the time it'll get scheduled, I'll be out of town on vacation. I didn't go to the gym at all last week. Partly because of my knee injections, but also because of my head. My doctor told me it could be from a couple different things. One being a seizure disorder, but I don't think that's likely. The other thing is something called Tic Douloureux. Basically it's nerve pain that's not harmful, but it HURTS. I'll feel better after the MRI and know that it's not something else.