What Causes Gush Of Vaginal Bleeding After Amenorrhea?

I had hematometra when I had ultrasound last week. No period for 9 months, bad cramps at each cycle. Then on Friday a massive gush of blood. I'm assuming this has cleared it. I have cervical stenosis after lletz and have had two unsuccessful attempts of d&c and now it seems to have cleared on its own accord. It's it likely to happen again?