Hcg levels

Je

Hi I am 7 weeks pregnant and have had two previous miscarriages so I went for the quantitative testing this time to make sure . My levels have come back way higher than last time but did not double with in the 48 hours only went up by 36% . My doc did a scan and managed to find a baby with a heartbeat . Which she was really shocked to find . Has anybody else’s levels not doubled and they have still done on to full term