Another question, can a horse be bred and come in heat 3 months in a row?
-Robin

Usually when a mare is bred she won't come into heat and won't be interested in a stud.... however, I have heard of cases where mares will, even though they are pregnant, act like they are in heat. I had one horse like that, even though she was a few months pregnant she acted as if she was in heat. Some people speculate that it is a hormonal imbalance that causes it, especially if it is a mare bred for the first time (but this wasn't a factor in my case as my mare had foaled before).

Have you had the mare vet checked? If you can have an ultrasound or rectal palpation done to check for a foal, it would be good, but even that isn't certain. I know of a few cases where vets have said a mare isn't pregnant, then later she foals.