Should I be worried?

So far this pregnancy has went okay. However, yesterday I went to the rest room and wiped and saw pink. It only happened that once (so far) and I wasn't cramping or anything yesterday. I went to the ER anyway because I am considered high risk, and when they did a transvaginal ultrasound they saw a little sac but nothing else. I thought I was over 6 weeks but turns out I'm 5 weeks. They said as of then, nothing was wrong, but that's not to say I couldn't be having a start of a miscarriage. I'm going to my obgyn today anyway, because I had an appointment but I wanted to see if anyone else had something happen that was similar but still had a healthy pregnancy.