I need some reassurance... please

I’m 13 weeks today and I woke up to some bleeding. I went to the bathroom and passed a blood clot. I went to the ER. They did an ultrasound and could not find any reason for the bleeding. They said baby was doing great and had a heartbeat of 180. Told me to come back If the bleeding doesn’t stop and I fill up two pads in a hour.

Has this happened to anyone before and you went on to have a healthy pregnancy?