I was told by a physicharist that probiotics may help with side effects of prozac (fluoxetine) do u agree?

No: Probiotics have many beneficial, if mild, effects on health. That they assist with Prozac (fluoxetine) side effects comes from the idea that they can reduce anxiety by supporting increased GABA in the gut, and therefore in the brain. (gaba in the brain reduces the excitatory effects of glutamate) but GABA does not cross the blood brain barrier. So more in the gut has no effect in the brain.

Possibly: If your side effect is nausea or loose bowel movements than a controlled release, multi-strain, high culture probiotic may be helpful. I an not sure how it would help for non-GI side effects.