Are diet pills safe

I want to loose some weight before my husband a I ttc. I'm 160 at 5"4'. I "should be 120".   I want to try something easy but in afraid I might do some permanent damage to my body or hurt my reproductive organs. Am I being crazy and over thinking this? 
Ps. I do work out. We just got married 4 months ago and I worked out almost every day this summer but I gained inches of muscle across my back. I don't want to get thicker!