Did they tell you why you were bleeding in the ER? I mean, could they see if the blood was in the uterus or not?
Some doctors would tell you that the cervix is extremely sensitive during pregnancy and if you dtd you may spot or bleed. My new doctor told me if this would ever be the case, it would have no effects on the pregnancy itself, other than just being scary/worrying to find.
However, in my case I had a few bleeding spells throughout my pregnancy so far. Ie, 3 times. They were all caused by a subchrionic hemmorage. They always tell you to rest and take it easy if you bleed. I've been placed on bed rest & pelvic rest for at least 10 days every time I've bled. But so far things have been fine otherwise, LO's growth and movements have not been affected at all by the episodes.
It is important to get it checked out every time you bleed. Have them also explain why you're bleeding and what it means. It can help alleviate your worries.