L.K.
I'd take him to the doctor to have him tested for diabetes. Diabetes is too serious an illness to wait out and see. At least if he checks out fine for that, there are other things you could look for, but having accidents and always thirsty are big warning signs for diabetes. And in a child the age of 4, SO MUCH can change in a year and a half. That is like a 40 year old saying, "well, I was tested for it when I was 25, and I was fine." Sorry to say, but schedule an appt. asap.