My dog is bleeding when she poops!?

I have a 12 week old beagle, and last night she got slammed in the car door, she yelped for a bit and then was limping pretty bad, but she walked it off within 10 minutes and today was playing for HOURS with my kitten. She is peeing fine, walking, eating and drinking but when she poops not only is the poop red but there is extra blood coming out, i don't get paid for 15 days so i can't get her to a vet!? DOES ANYONE KNOW WHAT THIS COULD BE!?