Could my cat be pregnant? how to palpate?

I have a cat, about 3 1/2 months old. I thought this was very young for going into heat but one day she began to go into heat. She was this way for about 3-4 days. Then she was just suddenly done. Then her personality changed greatly. She started eating more, being much more affectionate, sleeping more, and cleaning herself more. Her belly is a little poofy as well. She does not have any more symptoms of being in heat. I attempted to feel her belly to see if I could feel kittens but it just felt soft and squishy. No bumps or anything. Her have not changed. Does it sound like pregnancy or just a fake going into heat? How do I palpate for kittens?