The Horse Breeding - Worried about Prima

We Are Worried About Prima

Prima looks Pregnant.  Not a little pregnant, but really pregnant.  The docs at the clinic said she didn't take but she just keeps getting bigger and bigger.  We aren't feeding her any hay and only Progressive balancer (for a horse that is not pregnant).  The pasture is getting poorer and poorer as it gets chewed down and the nights get colder and the days get shorter.   The other horses aren't getting bigger and bigger.  Even Flicka is not so big and she is pregnant.  And Prima's big belly is lopsided, like it would be if there was a foal in one horn of  her uterus.  The last bit of suspicious evidence is that her udder is puffier trhan it should be for a open mare, I think.  It is certainly puffier than it was over the summer and puffier than Flicka's is.  Although Flicka is pregnant with her first foal and Prima has had three or four.

I have been working her harder than I would if she were pregnant and I will feel really terrible if it turns out that she is pregnant and we have been working her and not feeding her adequately.  But she is also fat.  Her butt is fat and her neck is thick so it is really hard to know for sure.  I will have the vet check her when he comes to do shots and worming in a few weeks, but if there are any experienced breeders out there who woud like to weigh in, I would be curious as to what you think.