Could be your saddle isn't fitting right, the stirrups may be too short, or they may be hanging "off" enough that you are going numb and hurting. Could also be, if riding western, that the stirrups need to be turned more?
Could also be the boot or shoe on your right foot is too small, or binding you and causing trouble, could also be the seam in your pants, fabric twisted when sewn, or your underwear even. All of those can, if out of whack cause the problems you are having.
Are you sure your stirrups are hanging evenly, don't just count the holes, stand in front of your horse and eyeball them to see how they hang. It is not uncommon for stirrups to be very uneven, due to the leather stretching more on one side than the other.
Make sure too, that your saddle is not turning some under you, getting off balance, which would make you put more force against your leg/hip/foot to keep yourself feeling even.
And sadly? Depending on the saddle maker, I've seen some saddles that are made unevenly too.
Try bigger boots, looser pants, checking stirrup length, and such.
Horses make me a better person.