I think my dog is pregnant but I'm not too sure?

Get her spayed now. You should NOT have left her out in the yard when she was in heat. That was totally irresponsible. Make an appointment for tomorrow to get her spayed. The vet will abort any pups if she is pregnant. It is the sane, sensible thing to do.l If you can't afford a spay surgery, you sure as hell can't afford to whelp a litter.