I got really, really sick in February when my neurologist gave me a new medication for my migraines, called Savella (its for fibromyalgia). My psychiatrist almost feel on the floor when I told her, because I am on Prozac, and Savella and Prozac should NOT be used together. I went off the Savella, and the Prozac as well, and my psychiatrist increased my antidepressant to 60 mg of Cymbalta. For the past two weeks, I've had fewer headaches, so I'm thinking the SSRI in the Prozac was a bad trigger for me.
Please be aware of any new medications you try and how they interact with what may already be in your system! And if you're on Prozac and experiencing constant headaches, perhaps you should talk to your doctor about any possible connection.