Miscarriage??

Kaitlyn

Woke up with cramps and spotting. At first it was light brown and now red. Still spotting. Cramps stopped. Went to thr ER and they did an ultrasound said it was no IUP and that my HCG level is at 21. I’m 4 weeks and 5 days pregnant. Is this a miscarriage or implantation bleeding? I’m unsure. And so are they. They want me to come back in two days to see if my levels change? As it was too early to detect anything on the ultra sound.