Black discharge @6weeks?

Ch

I was experiencing cramps and sharp lower back pain on my right side over the weekend and went to urgent care. The ultrasound didn’t show the fetus and they found small amounts of blood in my uterus when they did a pelvic exam. Cervix is closed and my HCG levels were 810 and I was measuring at 5.5. I have an appointment tomorrow for another ultrasound to hopefully be able to see the fetus and compare blood work to see if my levels have risen. Has anyone delt with this and had a successful pregnancy or should I be worried about miscarriage? I’m super nervous for tomorrow. This is my second pregnancy and I really don’t want to lose this baby. 🥹🙏🏼