Molly fish sick or pregnant?

[CastilloV]

I got my Molly fish about a month ago. About three weeks ago I noticed she had a belly and thought she is pregnant. She has been acting normal swimming around the tank and swimming with the other fish. I did end up moving my two Mollies to a different tank to prepare for the Fry. I have however noticed her pooping like this several times now and I’m starting to worry she is not pregnant and is sick. The last week she hangs around the water heater a lot and sometimes gets aggressive with the male molly when he constantly bothers her. Any advice or opinions would be greatly appreciated. This is my first time owning Molly fish and I’ve done a lot of reading but would love a second opinion from someone who has more experience. Thank you!