She looks like my mare... who I know is fat, and hasn't been running with stallions, and has already had her baby. And the mare before that I had, who was just fat. She's not really as light-type as you think she is.
With the amount of hay you have in front of her in those last two pics, plus if she's getting grain and pasture with no work? Then yeah, she's probably just fat.
No she gets no grain and I do work her for 30 mins daily with just lounging to get exercise. Plus I limited her hay access for a week with no changes, then I limited her grass with no changes then did a combination with no changes while still working her daily for 30mins. She could be just fat still though because she is a mini but she was never shaped like this. Her belly is shaped funny, not like a usual fat belly. But I guess I find out tomorrow at noon for sure, then I can rest with knowing a yes or no. I'm so anxious lol