Cat growing nipples?

Unless she is spayed she is pregnant, get her checked out by a vet, and book an appointment to get her spayed, you can do that now, before any kittens are born.

she's most likely pregnant. when she was gone for 2 1/2 days, she was holed up with a tomcat

Get her spayed, please. My Humane Society does spaying for $40 and adds $33 if the cat is pregnant or in heat, so that would only be $73. Not bad of a price.

I she isn't fixed and ran outside for a few days then yes she is pregnant.

It's really important you fix your cats because finding good homes for cats is so difficult. My cat did the same thing literally 3 days after I found her she broke the screen door and didn't come back for 2 days. She was getting bigger and bigger every day. The nipples will lose their hair and her belly will be hairless in no time. You don't have to take her to the vet 98% of cats have successful pregnancies. You can take her to the vet in about one month if you want to be sure everything is okay.

A pregnant cat is pregnant for 60-63 days. You won't see nipples enlarging on them unless they ARE pregnant.

Get her spayed, any vet can do a gravid spay.