Sitting issues

Hi all, how do you manage to sit for long periods of time ?

I'm having trouble staying still after 25/30mn. After that my right leg gets so numb, I've got to move it every once in a while. I'm not sure it really is an issue, but even if I try ti stay focused on my meditation while moving, it's always a distraction. Fyi : I sit crossed legs with my butt on a cushion.

Thanks !