Hi Jenna, she's likely pregnant. Cats are very good at reproducing. As someone stated above, the gestation period for a cat is approximately 64 days or 9 weeks. She looks like she's getting bigger and closer to having the kittens. Keep her inside if you can so that she doesn't wander off somewhere to have them. If you want to watch over the kittens, it's best that she has them indoors.
If you can't keep them, then try to find a local rescue group who can take them and find them a home. After she's had the kittens, they can be weened from mom around 8 weeks of age. If they can eat solid food, then they can find a home. Then you should get her spayed because she'll keep having kittens if not and then you will have to continue to give them away which causes more of a problem for someone else.
If you want to private message me for more advice. I'd be happy to talk to you. I work for a low cost spay and neuter service in Missouri. I could probably find you some resources in your area to help you out. You're very sweet to help out this little kitty mama. Wishing you the best in this new adventure!