Pregnant... Or not? Miniature mare question?

About 3 weeks ago I purchased a 12 yr. old registered miniature mare from a local farm. They told me they had purchased her as a bred mare but she never foaled so they assumed she was not pregnant. They guesses they have owned her her close to a year. Today the farrier came ut and was trimming her feet, when he was done he asked if she was pregnant. I told him no but it got me to thinking. I went online and read up on some symptoms. I can feel a thick waxy like substance on her teats but she is not bagging up. I read though that if they are on pasture, which she is, that they sometimes won't? Also when wboughtht her her stomach was very round and it has moved to where she looks thinner but Im not sure. She has been urinating all the time as well. The vet is supposed to call me back tomorrow but I was wondering if there were any tests that checked for late term pregnancies? Any help would be appreciated. Thank You!