What's going on!!

Vi

I had a miscarriage last month had pregnancy symptoms so decided to take a pregnancy test last week and it was positive. Did a blood test and hcg levels were at 40 so now I have to go back on Friday and test again. Well today I had cramps and I started bleeding. I think I'm spotting, the blood is very dark and there's a little of tissue. Should I even go back for more blood test because I now think it's just left over.