How many scoops r you taking..... cause pump 250 has a crap load of B12 in it and if you are taking 2 to 3 scoops your body many not used to it( able to utilize all of it) and you be "poising" your self which to much B12 cause involuntary muscle contractions. which you cant tell cause you are pushing so hard which leads to a tension headache. and like everybody else said it could be your bp and or lack of water.