Koda was doing the same thing at 12 weeks(Now I had called the vet about this and he kept telling me that she is too young for a UTI, not to worry.Probably puppy vaginitis. And it was, she had the long string of slime.), by the next week she was asking to go out every 20 minutes. By the end of the 2nd day of that it got really worse were she couldnt make it to the door and would dribble, that was the longest night ever. In the AM I took het to the vet, he did urine test and fecal (since she has had the constant runs since I got her). Both turned out fine, I was shocked. I told him something is wrong, she was doing great with house breaking and this constant squating and straining to get urine out was not normal for her. Ended up she has an inverted vulva and was licking it quite a bit. I didn't think she was paying that much attention to that area, she must be modest and did it in private..lol. He noticed it was red and irritated, thought there might be an infection. Put her on amoxicilan (sorry spelling)and it cleared up.
Also to reafirm an earlier post, I was giving "the best treats ever" every time she went potty outside. It worked so good she would try to fake me out and want to go potty all the time. Littl S###, chuckles, so I then only gave her a treat for thr 1st pee and 1st poop. Plus she had to do it withing 5 minutes or no treat at all. I ignored her the rest of the time, not even a glance. A great friend told me that and it worked like a charm. You should have seen Koda's look at me as she did her fake pee... it was like she was peeking to see if I was convinced. It was soo funny.