3 weeks is way long. If you havent started with the provera than you couls take a blood test. I dought that you are pregnate but it is possible that the tests just arnt picking up the surge. Do you have PCOS? it sounds like you either need a stronger dosage of provera or something else is going on. Either way you need to see your obgyn or a specialist. Good luck! and keep us posted.
they need to do some bloodwork to see where your hormone levels are and if it looks like you are ether going to ovulate or have a bleed, they need to give you more provera for you to start the clomid.
If you didn't start your cycle within 10 days being off provera, you should have talked to your dr immediately becasuse that is not a good sign.