Thoughts on whey protein?

i've been drinking whey protein pre&post work out as per instruction of my instructor, so i could absorb the protein right away yet a lot say im getting fatter. is the whey protein making me fat?LOL my arms and my legs particularly, im just tired of explaining to them that i dont think its fat but muscle underneath fat, some people even ask me if im pregnant. if i was, then someone call the vatican it's another immaculate conception. HAHAHA! these people are so naive..