What Causes Headache With A Low BP?

I have had a headache for about 3 weeks on the right side. It is an intense throbbing pain from the back of my head to my eye that wakes me up at night. Went to the doc last week and she gave me muscle relaxers and they do not work. I still have a CONSTANT pain in the side of my head. My BP was low around 60/30 -ish they took it several times and then told me how busy they were.... please advise.