Progesterone down but heard heartbeat?


I’m 7w5d and we saw baby and heard heartbeat two days ago. My progesterone has gone down though so I’m worried. A few weeks ago it was 20, then 19 the next week, and 16 this week. I’ve been on prog suppositories for four weeks. I know that a heartbeat is a good sign, but I can’t help but worry about my decreasing progesterone levels. Has anyone had something similar happen and what was the outcome? Thanks!