Strange bald patches on dog's legs, stomach, groin, and backside?

My dog Muffin is a three year old pitbull/American Staffordshire Terrier. She has always been healthy. I've noticed a few weeks ago, she started developing small oval spots on her belly. After a while, I noticed similar patches on her back legs and bottom/groin area. It has only started since it began getting warm this year. Also, she got a new carpet for her bed. She has never had any type of allergy, before. Her mother had always had some sort of skin condition where she would chew out her hair, but that is nothing like what is happening to my Muffin. Also, miss Muffin has been licking these spots alot... As far as I know, they aren't contagious, since Muffin often crawls into my bed at night, and I'm not going bald. None of our other dogs seem to have this condition, either. If anyone has any ideas as to what this is, your advice is much appreciated.