definitely call the vet as soon as possible, funny I am dealing with the exact same scenario. I bought my 11 yr old a buckskin pony last month, couple weeks go by and I notice her belly is starting to get bigger and somewhat lopsided(bigger on the right than the left). I dewormed her the day I got her so I'm thinking "what's up with this?" I called the guy I got her from he said he didn't know if she had been exposed or not, she belonged to a friend who had fell on hard times so he bought her and her 2 yr old filly. Needless to say the vet is coming out to check her.
Courage is being scared to death but saddling up anyway~~John Wayne