Why has my 10 week old Pitt mix puppy peeing inside when he hardly had accidents just days ago?

In the past few days my puppy has been starting to go inside. We still take him out every one or two hours and he pees and poops outside. Then he comes in and walks around and dribbles a little pee on the carpet or in the corners or my living room. Isn't he to young to be marking? He doesn't lift his leg he just goes a little. I catch him and get him and say "no" sternly and take him outside where he just looks at me. Just days ago he would only have none or one accident a day and suddenly its one every hour. He does seem to be drinking more but I still don't understand that small walking dribbles of pee. Should I restrict his freedom, or his water intake? Or could it be a bladder infection, if puppies can get those? Help!