OK Tash... pregnancy in cats lasts about nine weeks. Her nipples will become pink after about three weeks, so you would expect her to give birth some six weeks later. She will be far more sleepy and tired seeming during this period, she will become a lot more loving towards you (assuming you have a good relationship) and will gain some weight. At six weeks or so the nipples will grow in size and become filled with milk, she will probably be hungrier than usual so give her a bit more high quality food (not too much) but expect her appetite to diminish just a few days before her kittens are due.
I suspect you will soon be the proud parent of a whole batch of new kittens ! If you are lucky, she will have them in a place where you can see that they are ok and healthy, just don't remove them from her just yet. If you do move them, she'll probably just scrub them clean and put them back where they were ! I wouldn't advise you to touch them yet either, she might get a bit miffed at that !
When she has had her kittens, she will be tired, so make sure she has plenty of food and water (and possibly a litter tray) near cos she is going to have her hands (paws?) full for a few weeks...