Vaginal bleeding and pain (pls help)

Okay, so this is happening to me the second time. A little bit of blood is coming out my vagina and my uterus hurts. Today is March 25 and my period ended on March 20/21. This also happened to me last month, I had my regular period and then few days later this happens. I didn't have sex and I absolutely can not be pregnant. If you have an advice please leave it in comments.