Bleeding during pregnancy 18 weeks?

Just returned from the hospital, from what I thought was going to be the worst. When I went to the restroom I had some blood on the paper (TMI sorry). Of course I freaked out, at 18 weeks I didn't expect to find that. Went to the emergency room and they checked me and the baby's heart and said everything was okay. They said it's probably bleeding from . We had last night and it was a bit rough. Now I'm really scared, even though I heard the baby's heart beat and can feel the baby moving. My last pregnancy ended in a still born, and now I'm a bundle of nerves. I didn't have any cramping until after my exam, is that normal? No cramping at all during the day, felt normal as I usually do, except for finding blood. It's now kind of heaver but I think it's a mixture of the lubricant they used for the exam. Has anyone experienced this? I need to put my mind at ease. How long will the bleeding go on for? If it goes longer than about 2 days should I get concerned again? Hospital never said how long it should last, just told us to put on hold for a week.