Why did my head hurt upon orgam?

My teeth have been hurting me and the radiating pain has been giving me headaches. Ive got most of the dental work taken care of but Ive still been getting headaches. Two days ago I had sex and a crippling pain shot from the back of my head to the right side right as aI orgasmed. Yeserday I had oral sex an when I orgasmed I was fin but earlier that day I had a headache as well. Finally today I was having sex and right before I came it started to hurt so much I didnt even want to finsh. What could be causing this and how important is it I go see the er?
--------------------
I know if I already have a headache, activity of any kind, including sex, makes the headache worse. My only guess as to why it didn't happen during oral sex is that your level of activity isn't the same as when you have sex. If your teeth have been hurting, your sinuses may be swollen. I actually was having teeth pain problems once and i went to my dentist. There was nothing wrong with my teeth, but he told me that there is a nerve that runs under or through your sinus cavity. So if your sinuses are swollen, it can press on that nerve giving you the tooth pain. So you may want to go to the doctor if you think it may be a sinus infection, or having allergies may cause that too.
Source