I think I am miscarrying but not sure.

I would be 4 weeks 4 days today. I’ve had spotting intermittently since the day after I tested positive. I had a blood test to confirm pregnancy on 7/10, came back positive and my beta hcg was 21. I continued to have intermittent spotting and on 7/16 I passed a small clot so I went and had another beta hcg to confirm rising levels. It had only risen to 51 in 6 days. The bleeding hasn’t been heavy at all but is more mucous like now. I’ve heard miscarriages should be similar to a heavy period in terms of bleeding. Mine has not been like that at all. My doctor suspects ectopic or miscarriage. I go in tomorrow to have more lab work done and to see the doctor. Has anyone else experienced anything like this?