Pregnant?? or.....?

I haven't been here in a long time, but I have a question that I need answered. We recently moved out to the country. We literally live in the middle of no where. We only have 3 neighbors, within a mile or so. A couple days ago this tiny cat appeared on our front porch. At first I thought it was a boy.

"He" is the friendliest little thing. Purrs up a storm whenever you pet "him", comes when you call "kitty, kitty!" Doesn't give a second glance to my chickens, and is only mildly annoyed by our dogs (hissed and puffed up the first day, but the next "he" gave the dogs head butts and rubbed against them).

Last night "he" layed on "his" side and I noticed that "he" had darker patches of fur around "his" nipples. This cat is white with grey spots (some may have seen pictures on my facebook page). The patches around the nipples are stained a light brown. Today "he" was letting me pet "his" belly, and the nipples are enlarged. I took a closer look and realized "he" is really a she!

I have NO clue how old this cat is, but from the look of it, a lot of cats around here are small. Our neighbor's cat, a male, is itty bitty also. I don't know if this cat has a litter right now, somewhere around here, or if she had a litter at one time and is pregnant right now. Her belly is swollen, and has increased in size in just the few days since she arrived here. I tried feeling for movement, but she wouldn't hold still long enough for me to notice anything. I tried expressing some milk from one of her nipples and nothing came out (yes, she is that friendly...she just purred away).

She is SOOOOOOO skinny, other than her swollen belly. It makes me think she is pregnant, b/c she looks like a cow does when they are pregnant, if that makes sense. I don't know if she belongs to anyone around here, but since she is so thin I have been feeding her anyway. I figured a little extra food wouldn't hurt. (If I shouldn't, please let me know.) I have since seen her every day. She loves the attention, and my son loves her. We always make sure we wash our hands as soon as we come inside, just in case. She keeps wanting to come inside.

Is there really any way for me to tell if she is currently pregnant or if she is just nursing?

Here are a couple pics of her:

Yes, she always keeps her head tilted. I figure it is a left over side effect of some sort of vestibular problem. It is gradually getting less and less tilted.

I don't think she is pregnant anymore. I think she was just SOOOO starving that she was gorging herself. Now that she is getting fed regularly, she doesn't get bloated like that. She is starting to put on some weight. I'm pretty sure she has kittens somewhere around here, though. I've given her scraps of raw chicken a couple times, and both times she carried it off and down the road.

We've adopted her. Well...she pretty much adopted us. We'll be getting her spayed, but not until I'm certain she is no longer nursing kittens. I don't want to bring her inside until I can get her into the vet to be tested for FIV/FL b/c of our other cats. She stays on our front porch almost all day now, except I think to go feed her babies. She tries all the time to get inside, though.

Thanks!