confused?!?!?

Ok so I started provera in may and had a period may 19 and not one in June so Friday I aw my doctor and he ran blood tests and said my hcg was negative and I didn't ovulate last cycle so they would give me provera again to start my period well I picked up my script today and have yet to take it and when I went pee, I look down and there's brown discharge a normal sign my period is starting?!?! Could he have been wrong or can it start on its own that fast????