Fetal movement at 21 weeks?

Hi! I'm 21 weeks pregnant. Up until Friday I was experiencing a LOT of movement however it was lower down in my pelvis, right about at my pelvic bone. Now, it feels much lighter (I can still feel it but it's not as obvious) but it's higher up. I know the baby moves up into your abdomen but I thought it wasn't until later on like week 24. Has anyone else experienced this or can offer an explanation? Thanks to all who answer!