Coop'sMom,

I hope it's not an infection or other illness. 13 wks is still
pretty young to be totally reliable about housetraining. Maybe
he's just regressed a little bit. Goes he act any different lately?
Maybe he should just be restricted to the kitchen for awhile,
or kept on leash near you when he's allowed free time around
the house. Let us know what the vet thinks if you should
decide to take him there. Good Luck with this.