My cat was fixed about a year ago and was a indoor at the time and when she fully healed she started going outside now I have noticed that her abdomen has increased in sized but I can tell it not just fat it is more of a "solid" bump. I researched signs of pregnancy in a cat and she is showing a lot of them. Is it possible for her to be pregnant? Please let me know I want to be prepared. Thanks so much!

If she was actually fixed, then the vet removed her uterus and fallopian tubes, which would make pregnancy impossible. If she is pregnant, it means the vet charged you for a procedure they didn't actually do.

Assuming the vet actually did the procedure, it is not possible for cat to be pregnant

Properly spayed, no, she cannot be pregnant, however if you are feeling a solid lump, then it should not be ignored. Other things that can cause a "solid" lump, constipation, a tumor of some sort, enlarged organs, could be that there is something else going on that needs to be addressed, or it could be nothing, but I would take her in for a check up if you are concerned.

A properly spayed cat cannot be pregnant. It's not possible. So, if she was properly spayed, no, she's not pregnant. Pregnancy isn't the only thing that can cause weight gain and a hard lump. Time to go back to the vet to find out what this lump is.