How can I tell if my cat is prego?

Ok to start this out, I don't need any lecture about how the cat needs to be spayed ect...I KNOW THIS!! If she is pregnant then she will be spayed afterwords and if she's not I will be making an appt with the humane society to have it done..that said, shortly after I recieved this cat from a friend she managed to escape out the front door and evade me for several days..now it's about a month later and her little nipples have grown a bit larger and pinker and her belly from the sides is bulging a bit, also all she does now is sleep and eat..do you think that sounds like she's preggers?