Do pregnant mares not like to be ridden?

We've suspected that my mare is pregnant from the moment we got her. All she's been doing is getting bigger and bigger, I've only had her for about 2 months or so. She doesn't like it when I brush her belly near her udder and hates when I pull on the girth if we rid (there are other reasons we think she's pregnant but this isn't that kind of question) Since it's winter and our winters are pretty harsh I decided I'd only ride her bareback in the arena. I've only ridden her bareback maybe twice. She's fine when I'm on but mounting is such a struggle! She moves and jumps if I touch her belly with my foot the slightest bit. I can only walk her because if I put pressure in my heels on her she bucks. Is there any way to make her stop or if she's pregnant should I not even ride her?