I am 53 years old and Zenical done that to me - i take propananol and took Xenical for 2 weeks and never got off the loo, I was hungry and after 2 weeks I gained 2lbs and spend the following months with belly pains. See your doctor but i don't think it has anything to do with the Prozac
Though quite successful in controlled drug company trials Xenical/orlistat, which is twice the dose of Alli is very disappointing in the community. Like most people who try them you will not lose much weight. You would notwithstanding receive diarrhoea, foul smelling liquid stool, abdominal cramp, occasionally faecal incontinence and wind. To lose weight you eat a little less and increase your exercise.
I think you should switch from Prozac to Pristiq. You are probably de-sensitized to Prozac by now. Btw, I hated Zenical. I don't think it is used much anymore. The studies showed weight-loss to be minimal.