J., my ob/gyn started me on Zoloft during my pregnancy. I was almost 8 months when my husband decided he wanted out of our marriage...lousy timing!...and I was unable to eat and lost 8 lbs in one week. I stayed on the medicine through the remainder of the pregnancy and the divorce, about a year and a half. He said it was safe for me and my son, who was exclusively breastfed.
My son does have Sensory Processing disorder, but they don't really know what causes it. One seminar I went to said they do feel stress has something to do with it...so that could be attributed to the breakup of my marriage and the divorce process. And if anything, the Zoloft helped me deal with the stress, so I imagine it his sensory issues could have been worse! He's 9 now, and you'd never know there were any issues at all, since he and I have learned how to deal with the things that bother him.
Was it your ob/gyn who prescribed the Prozac? You need to talk to him. Like any medicines, sometimes you just have to take them. All drugs have risks, you just have to decide if the benefits are greater than any potential side effects.