Don't know if my cat is having kittens?

Hi, My female cat is now a little over a year. She went in heat and got outside. My neighbors reported seeing her have sex with other cats. Approximately 3 times. Apparently there is suppose to be redning at the nipples around 13 days. Also they are suppose to be bigger. I never noticed my cats nipples before until now. But they are not redning. Is she pregnant? Please tell me what I need to know.

Unfortunately, there's really no way for me (or anyone else) to tell if a cat they cannot see is pregnant over the internet.
   
You can either wait around and watch for obvious signs, or take her to a vet to have her tested.
   
I would also strongly suggest you get your cat spayed asap. It will keep you from getting stuck with kittens as well as stop her from going into heat (which is totally obnoxious)