I need help. Only 22 years old. female.

Hi so ive had a peeing issue for about a year or two. Everytime ive gone to the doctors they say i might have an infection due to the white blood cells in my urine and I get the medication and finish it. First two days the urine calms but goes back to the fequent urination. I dont have an infection and its not possible for two years.. Doctors dont know what it could be and I keep getting white blood cells in my urine. My sugar iw fine no diabetis. I pee up to 30 times a day probably more. At night I pee all night long every hour full stream I can never get a good sleep and I just have to pee all day everyday. I dont know what to do. What I notice is that when I have to pee and lets say I hold it because im tired of getting up itll start to give me a little burning sensation if i hold it to make me go pee and then im reliefed. No burning other than if i hold it.Im only 22 years old. Female.