Hcg levels - worried

I went in for blood work for my hcg levels and I was at 59 and then five days later I had another blood test and it was 67. They think it is very low and that I am not pregnant so my obgyn is taking me in early to double check. I had a d and c in March and had my first period in May and got all positive pregnancy tests. I'm worried there's something wrong. Has this happened to anyone and what was the outcome?