Bleeding during 1st trimester?

Yesterday at 12wks3days while finishing up an echocardiogram I got up and I felt a hush of something so I right away pulled my pants down and put my fingers to touch and it was blood. I started panicking since I’ve felt this before with my last two miscarriages. They rushed me to the ER and I had a reg ultrasound and a vaginal one. Thank god the baby was good and moving around. Heart rate 157 ❤️ they didn’t tell me exactly why my uterus was bleeding but they checked my cervix and it was close and my hcg levels were good. I’m so thankful my baby is good. Now the bleeding has stopped. Lasted like an hr. Only brownish blood at the end. I’m so scared and on bed rest today until Nov 1st which is my next appointment. Has anyone experienced this?