Serious question...

So please explain to me why I cannot for the life of me ride a dick? And like when a guy asks me to do it I just get embarrassed and idk what to do! I can only do it while like squatting if that makes sense but i can’t do it for long cus y’all know that shit gets tiring. I feel like my thighs are too big and it’s just hard to do it. Does anyone else have this problem?