I Have A Vein On The R/s Of My Jaw

I have a vein on the r/s of my jaw that is swollen and painful. have been to my regular dentist and a endodontic dentist and both say nothing is wrong with my teeth. when it began I had severe headache and jaw pain. the pain is subsiding now but is still sore. during this time I had a spell where I was dizzy, nauseated, then passed out. my blood pressure was really low. it hasn't happened again like that. when I yawn or take a deep breath I can feel nerves in my tongue and jaw ache. thoughts?