11 Month Old Girl Pug, Whats Wrong With Her?

She's almost 11 months old, Black Girl Pug, very healthy and active. She's an indoor dog that is trained to go to the bathroom outside, & Our yard is inclosed and has not had any interaction with any male dog. She has played with 2 other girl dogs (molly and kizzy) but thats it. But lately i noticed her nipples look like utters. and shes ovbiously not pregnant so what else could it be? Anything That Would Help, I Would Appriciate It!! :D