How to tell the difference between baby sitting low and head down vs dropping?

Sarah

My last ultrasound at 30+5w baby boy was in the perfect position, cephalic position and right above my cervix but cervix was still long and closed. Would that be considered dropping or just positioned low, and how to tell bump wise if he’s just sitting low/I’m carrying low or if he’s officially “dropped”? 33+3w currently and been getting a ton of back pain out of nowhere this past week and lightning crotch in bed at night has gotten worse.