Bleeding in 1st Trimester

So I'm almost 11 weeks and since about 6weeks I've been spotting/bleeding. Well at the first ultra sound baby was healthy with a strong heart beat. Last Tuesday I fell and the next day started bleeding a little heavier, well my doctor is so busy he couldn't get me in so he sent me to the er. They did an ultrasound and the baby was fine and again had a strong heart beat. Said they couldn't figure out why I was bleeding. Now since yesterday I've been bleeding heavy almost like a period. It's enough that I've put a pad on. This is my second baby and I'm scared. I never bled like this with my first. Has anyone experienced this and not miscarried?? or is it a telltale sign that it will eventually happen?