Possible ectopic pregnancy?

I am at 3 to 4 weeks pregnant, no more than that, and had to go to an emergency room Monday night because I had severe pain in my abdomen after having with my husband. Found out I'm pregnant but they said it could be ectopic because of the pain. The pain is now gone (it was gone the next day but I've felt sore/tender in that area for a few days) everything feels almost normal now. They even gave me an infant bereavement card which really scared me!! Has anyone gone through this and what can I expect? They still don't know what caused the pain... I have had to get blood drawn every other day..