what's up?

My female kitten (a little over a year old) has recently gotten outside. Her stomach feels like it's getting bigger, but she is still going into heat. Is this possible if she is in fact pregnant?

Yes.   they can have two different litters, about three weeks apart, both litters may be healthy with a little luck.

This almost never happens with regular, serious breeders, as they have exact count on matings, but for "oops" moggie owners its not unique.

My guess is she IS "in this way", and also, in heat.

So DONT let her out again if you dont want another litter.

What you do with this litter you must decide yourself: take the spaying now, OR if you want to have a litter, spay her later when the kittens are weaned.

In both cases a vet visit is in order, if nothing else so deworming of her, and planning on deworming and care of the kittens.    Dont   make any vaccinations on her now, if she is to have this litter.

It is wise to have a contact with a good vet.  Being his regular paying patient, its much easier to phone and ask advices even when his clinic isnt open.    And such things do happen when you have pregnancy and delivery.

Good luck!