What Causes Intermittent Bleeding After Taking Depo Injection?

I had 1 injection of depo that wore off Dec 30th (did not want another shot). In the beginning of January I stood up 1 day and had a gush of blood felt like I wet myself. After an hour bleeding stopped. This week it happened again during intercourse and stopped after an hour. Does this mean anything? I don t have any health issues that I know of and this has never happened before. I never spot or have problems with bleeding.