Is my fixed feral Preggers?

Hi I had four ferals and mama TNRed about 5 months ago.  I feed them and interact with them at work on a daily basis. The kittens are app. 9 months old.  I wormed them with over the counter wormer about 2 months ago.  I noticed the one of the females (the only affectionate one)  belly seems a little rounder then the others.  She isn't the big eater of the four either.  Is there a possibility she is preggers?  I took them to a community cat rescue that works with a few vets that have been doing this for years, TNR that is.  So I am hoping this is not the case.  I realize some cats can get some weight gain when spayed.  We are in the winter months here so they are not as active.  Is there anyway I can tell or signs to look for so I don't have to recapture her and stress her with a vet trip to be sure?  The weight is in the center of her tiny body not towards the tails end of her belly.  Hopefully I am just being overly worried.  Thanks for any insight.

I'm thinking she may still have some worms.  I'd check that out first.  Fingers crossed that's it!

Thank you. Is there a good wormer I could use? I just purchased one from tractor supply?

I have only ever used Drontal, which I got from the vet.  I know different wormers kill different worms, so you might want to ask you vet, just to be sure.  The stress would be worth it to me.

Try Imathal.   I got it at my vet's for my semi feral fosters.   It's cheap (6 doses for $20 at the vets) and I think you can get online without a RX.    Best part... my kitties ate it right down when I mixed in baby food!    Works for round and hook worms.   You need to give 2 doses 3 weeks apart.

Thank you for all of the replies.  Better get started does anyone know anything about diatomaceous earth?   Would that be something good to work into their diet?

It does help but it is better for maintenance.  Make sure you use only Food Grade - the other stuff is used in swimming pool filters and is loaded with chemicals.

Sprinkle a pinch on their wet food - it is pretty tasteless, so they shouldn't notice it.  I only used it once a month or so, especially in the summer.  It also helps with fleas as it kills tape worms.

Nice thank you!  I will get a vet given wormer first then follow up with this.  I did my research on it.  Definitely will get the food grade stuff.  Thank you again for the help!