Is my dog pregnant or sick?

I have a schnauzer, mixed with wiener dog, well she's been left with my father in law for a little less than a month, he has a boxer. Well, I got her last night, and she is heavier and looks bigger in the rib area.. I haven't seen her in a month, and I don't know if something is wrong with her, or if maybe shes pregnant? She was so clingy to me, shes my baby and since I got her, she still follows me around but when I call her over to cuddle, she won't come anymore.. shes just acting different.. also her boobs are bigger... lol any ideas?