Provera frustration

I'm on my second cycle of provera. Last time my period started the day after my last pill. 10 mg for 10 days. And lasted 7 days. This time (same dose) it started 3 days later and I'm on cd2 and its stopped. Has this happened to anyone? My lining was still thick after my last period. It showed on an ultrasound so I really need this to work out.