Can't Tell If My Balloon Molly Is Pregnant Or Just Fat

[Edagger]

I bought her on October 5th or 6th and i picked her because she was the "most pregnant" looking in the tank at Petsmart
she hasn't given birth yet and i don't know how long she could have been pregnant before I bought her...

I was hoping someone could help me figure out if she really is pregnant or just really fat lol
I took some pictures- she HATED it and kept swimming away but I got a few...

please let me know