I have gone on and off prozac (fluoxetine) several times over the past few years. is this changing my brain chemistry? is it bad for me?

Not really : There is no evidence that starting and stopping antidepressants have a negative effect on the brain. However, if you have taken the medicine for periods of severe depression, perhaps you should stay on the medicine to prevent a new depression from happening. Major Depressive episodes are associated with negative effects on the brain

Better to treat: Hi Amanda, there is controversy about this (particularly outside the scientific community). Within the community, there is agreement that depression itself changes the brain in undesirable ways, can be debilitating, and warrants treatment. If your depression is mild/moderate, and you prefer not to take meds, you can find significant relief through life style changes and therapy. Take good care.