Verified answer

She most likely has been dating another cat,going out at night is when all the males are just waiting, and possibly in your garden lying in wait,it only takes moments but i think as she is obviously not spayed and been out a few times then the deed will have been done!,

so now when a cats pregnancy starts to show,meaning wide at the sides then she is 5 weeks or over this is because unborn kittens skeletal structure are not formed enough to be visible,so check her belly look at her direct from above,is she slim all over and wide at the sides?,

then that is a clue,then check her nipples they go a darker shade of pink and the further along in pregnancy the darker they go,and cats do become much more homely as they get tired quickly carrying around a big tum,another way is feel her belly you should be able to feel the kittens heads,they would feel like little bumps that move when touched,

and another way is place your ear to her belly,a pregnant cats tummy makes a constant bubbling sound,this is the amniotic fluid surrounding the kittens,and a cat who is pregnant hate being held as their tummy is sensitive, but before the birth this changes they become so loving all down to hormones,so if you suspect a pregnancy then set up a nesting box ready for her now,its never to soon,

i have seen over 500 kittens being born due to foster work so have seen many pregnant cats,and all the things i mention are clues they gave,here is a link to help further all about the pregnancy and even the birth itself,so you can be prepared,

http://www.sniksnak.com/cathealth/howto15.html

21 days after the breeding or mating her nipples will turn a bright or hot pink. Then you have 6 weeks left.

R P CAT