I am not a dr however I do know that anti-depressents and anti-anxiety meds can help with headaches and anxiety and stress can cause headaches and a lot of them should not be stopped quickly and their are times that it takes awhile for them to actually do their full thing as I have been on them before, I suffer quite a bit with migranes and they cause nausea and about the only thing that really helps me is that if I take a immitrex with a promethazine and lay down in a dark room and sleep for 2 to 3 hours, I am also on topomax which I do not really care that much for(too many side effects). You should contact your dr an let him know what is going on, he might recommend something else for you!
Also make ssure you have had your eyes checked recently, another problem a lot of people are having, especially with sinusus and all.
Good luck!