I went through the same thing at 6 weeks, I woke up one morning, went to the bathroom and had blood rush out of me with one clot. I went to the ER and had an emergency ultrasound and bloodwork done. In the Ultrasound, the technician found a cyst on my ovary as well and said they can cause bleeding. I was also told, that around that week in pregnancy, something called implantation happens. It's where the sac (or whatever the fetus is in in that stage) attaches itself onto the wall of your uterus. It can cause bleeding in some women. I had to go back and have ultrasound in the next week, and she finally saw a heartbeat I'm my little guy and he was a-ok! Oh, and I'm 24 weeks now and my ovarian cyst frequently causes little amount of blood during urination. It's only like a pink colour and doesn't persist. I know blood can be scary but just remember not to stress..stress makes your baby stress :) hope my story helps! Good luck!
5 weeks is a little early sometimes to see the baby during an ultra sound call your doctors office and tell them what happened and they will probably see you right see away