Could my cat have gotten pregnant?

My question is. My cats been in heat since sunday-monday night. Anyways she got out last night not sure how long for. But since last night. She hasn't really bothered doing the usual treading or meowing to get out. And when I stroke her she normally lifts her bum up. But since last night she hasn't. I dont want (get her spayed or anything like that please ) thanks for any GOOD answers