my (20f) hips won’t move during sex

I’ve been getting annoyed and frustrated about this recently because I feel like it should be easy, and I’m embarrassed. Anytime I have sex, I rarely get on top because my hips literally will not move fluidly. I’ve done gymnastics and cheerleading all my life so it’s not that they’re too tight or I need to stretch more often. Even when I workout I can never do RDLs because my hips don’t hinge correctly. I’m wondering if anyone else has/had this problem and what you did to fix it? I just want a normal sex life 💔