I've measured oddly through this pregnancy. For a while I was ahead 2 weeks, then I was right on, then I was behind 2 weeks, now I'm right on again. I was consistently measuring 2 weeks behind with my previous 2, they came 39w6d and 40w4d, 7lb5oz and 7lb4oz. I gain usually the same throughout. I'm actually a little bit behind this time, and somehow, over the 2 week break in between visits, with Thanksgiving in between, I lost half a pound. And baby definitely could've dropped a bit for you too. With my first (only time I dropped prior to labor), I was 36cm at 38wks, then next visit I was 33cm. So DEFINITELY could be that you dropped.
As for the movement decrease... maybe start doing kick counts at the baby's general awake time and see how long it takes to get to 10 kicks. I know my midwife wants at least 10 kicks within the hour. I get mine usually within 4 or 5 minutes, but I've got a crazy one. Sometimes it's good just to have a general guesstimate, since sometimes it seems like they haven't kicked much, but it's still within normal range.
For the cramping... since you're 37 weeks, I wouldn't say much unless they seem to be following a good "labor" pattern. I've been cramping for the past 2 or 3 weeks, that haven't led to labor, but I'm sure they're doing something to my cervix. Just gearing up I guess!
Hang in there!