What's wrong with me?! I need help...

So I'm going to start off by saying that I have PCOS. My doctor has me taking birth control to regulate my periods and to help my ovaries. It's made me very regular and I haven't had any problems till this month. I'm going on 3 and a half weeks without a period... My doctor refuses to help me understand why this is happening and I've taken 5 tests and they all day negative. Can anyone tell me what they think is wrong??? Thank you