Now I'll worry my whole pregnancy!!!

So I woke up last night around 1:00 am and felt like I peed myself. I jumped up and went to the bathroom and I had a lot of blood. After I used the bathroom the bleeding was completely gone. I went to the ER of course freaking out. They did bloodwork and everything looked great and they also did an ultrasound and I'm measuring right on at 15 weeks and a few days. The baby was very active and had a good heartbeat. I just got no answers about what happened at the ER except two possibilities it COULD have been and that if the baby isn't at least 24 weeks it wouldn't have survived anyways. (Which I knew, clearly). I called my dr today and they went over all my stuff done at the ER and said everything looked great just to keep my appointment for Monday July 11th to be checked out. I just know I'm going to worry the rest of my pregnancy and not be able to even enjoy it. Did anyone else have and experience like this? If so what was the cause?