Could my pregnant cat not be pregnant and actually have worms?

My cat Basil was "rescued" by me, my mom and my sister. She came from a friends property along with 2 adult females, 2 eleven(give or take) old kittens, and her 2 brothers. we fixed the 2 adults(one had a busted ovary and would have died without the surgery) and brought them back to our friends house. He lives on a mountain far away from any other houses or people. the day we meant to fix basil, and her 2 brothers, Basil and her brother Poppy got out of the house for the first time and we only fixed Basils other brother Thistle(and the 2 adults). I am not positive on her age but I am assuming it is something around 7 months(I'll add pictures). She has been VERY affectionate and had a little morning sickness, and her stomach is quite big. My mom doesn't believe she is pregnant because her brother mounted her, and she thinks she is just bloated from having worms. I don't think it would be possible for her to not be pregnant because she was around so many male cats for all her life. I would also like to know how old she looks, I can attach a picture of one of Poppy for a more accurate size. If she is pregnant then her growth would be stunted I believe and she is a bit smaller then Poppy. Basil is black and white with a white face and black bangs. Poppy is black and white as well and has black covering one eye and the other one is white. Basil should of had her first heat already and if she is pregnant she would have gotten pregnant on it. I will answer any questions you have.

Thank you
-Charlotte

I forgot to attach the pictures.. good job me.. anyway, the first pictures are basil and the last ones are poppy.

The ones of Basil didn't post so here are some more of her.

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This one didn't make it to my last post. It is Basils stomach, dose she look pregnant or does she probably just have worms?

@StefanZ I am a newbie, but I have been reading about and I am wondering if you knew anything about this.

If your cat was not spayed and she was mounted by an intact male, you can be sure she is pregnant.

When did she get out of the house?

Sarthur2 she was outside with many male cats before I got her, she was probably around 6 months when she became an inside cat with her two unfixed brothers, who we thought were girls at the time. One of her brothers got fixed but the other,Poppy, has mounted her before. should I separate them in case of 2 pregnancies? Why would he be mounting her, could she be in heat?