13 weeks heavy bleeding

Just wondering if anyone had any past experience. This is my 2nd pregnancy and I have an 18 month old. 13 weeks yesterday I went to the bathroom and had blood in the toilet. We went to the ER expecting the worse. Was changing into a gown and bled all over the floor, it was heavy. However, they did blood tests that came back normal and when we did the ultrasound we had a happy active baby girl with a very strong heartbeat. Unreal. They didn’t have any answers for me except to rest and get an appointment with my OB on Monday. As I’m laying here trying not to stress I’m just wondering if anyone has had experience with it being something harmless or an early miscarriage. 💕