HCG still elevated...

Sara
It has now been 18 weeks since we had our ultrasound that showed no heartbeat. I was 8+ weeks along at that time, but things stopped growing at about 6 weeks. My midwife has been following my HCG levels ever since; they started high and have been very slowly tapering off. My last check was a month ago (60) and today it was 23. Almost there. 
Has anyone else had things take this long???