I have been on Effexor XR 150 mg for 2 years and have only had mild side effects including dizzyness - no headache.
Nobody knows because they're not you. My own opinion is that five weeks is a long time to suffer the same side effect; usually they shift when you first start a medication. Since Effexor is a difficult drug, I'd probably taper off and try something easier to take and to quit. But that's just my opinion.
Thanks for your oppions. I am going to see my doc today about this. Much appreciated.