I found a cat that wandered into my yard yesterday. She has a huge belly riding very low to the ground. She has decided to lay under my deck and has been there about 16 hrs. She is just lying down and rotating her position every few hours. She seems to be very lathargic. I think she is very pregnant but am not sure if she is ready to give birth or if she is indeed pregnant even though she definitely looks it.

What is your question?

A similar thing happened at my mothers house, a pregnant stray decided to take up residence under her house.

She put a nest box under the house for her with blankets, water and food.
Don't get too close to her, you don't want to spook her and make her think that the area is unsafe but if you can try and provide her with something a bit more comfortable and safe to give birth in.

Can you see if she is wearing any tags or a collar? She may have escaped and someone is looking for her.
You can also try encouraging her to stay but putting up some flyers in your area.