Low HCG but still pregnant?

Brittany • Married💍 1 amazing little girl 7-9-19🤱🏽

I just want to know if anyone here has ever had low HCG levels with a healthy successful pregnancy? Little back story... I had my blood drawn 1-29-18... was only 42.5 and I was “supposed” to be 5 weeks at that time... 1-31-18 HCG dropped to 32.....my dr told be I would be miscarrying.. 2-1-18 started bleeding I was devastated... 2-6-18 had an ultrasound to check everything over everything looked normal with ovaries cervix uterus etc but there was no fetus present as I was just bleeding... dr told me she wanted to continue to monitor my HCG levels through out the week.... however blood drawn again 2-6 level still 32..: and now today 2-13 my level is now 65... anyone had this happen and be pregnant and carry to term? A hidden twin? Anything? My dr said she is puzzled and don’t have any answers for me right now until she sees another ultrasound next week. Any thoughts welcome