Can baby move up after being engaged?

Bethany
Im 38 weeks tomorrow and baby has been engaged into my pelvis since 36 weeks i was also thinned out at last appointment. I carry very low and have the whole time so i havent had heartburn at all (thank god) last night i just started to feel very weird kinda naseous and last night i got heart burn so bad i was choking still have heartburn but not as bad i guess cause im not laying down. I also noticed my bump is so hard and high up as if shes moved up is this possible? If a baby is engaged can they move back up and can my cervix reverse the thinning i had? Weird question just curious i wanna go forwards not backwards! And this is my first