Being put on Progesterone as levels are low and baby is measuring small! Anyone been thru this?

So I’ve been spotting on and off for the past nine days or so I went in for an ultrasound yesterday and blood work.

I am 6w2d, but scans show more like 5 w. My hCG levels are high enough to support at six weeks. However, the ultrasound does not match. They said my progesterone was extremely low and needed to be put on it relatively quickly. I’m going in next week for another ultrasound and more blood work. Have any of you been through this and still carried to full term