I assume you have a psychiatrist who presumably knows about this better than we do. I've heard of combining ssris such as Prozac with Wellbutrin to deal with sexual and weight gain side effects. But you could also try a different med; it could be the Prozac has stopped working after all these years. They do poop out for many people. If it has pooped out, it makes no sense to take two drugs when one isn't working anymore. But your psychiatrist is the one to start this conversation with.