Really? Then why are you ASKING about how to figure out if your mare is pregnant or not?
THE ONLY WAY TO KNOW FOR CERTAIN IF YOUR MARE IS PREGNANT IS TO MAKE AN APPOINTMENT WITH A VET.
I can't believe all the people on here who have horses who think calling the vet for major things like pregnancy, mouth problems, back pain, and leg issues is out of the norm. Either you're too cheap, too poor, or don't really care about your horse's welfare.
If you can't afford to care for a horse properly, and that means calling a vet out when it's necessary, then you shouldn't have one.
Owning a horse isn't like owning a car. They're living, breathing, feeling, sentient beings who deserve proper medical, dental, foot, and feeding care.
I am also just curious-what is the white powder your mare has on her face? It looks to be in her feed bucket?