i have a physical problem in my brain where i cant feel half the pain normal people do ha. thats why i get hurt so much and then realize a week later...
but try stretching your legs more, just to get them loose and then after your done too. it helps alot with pulling things and that..
The reason for this is because you are leaning too far backwards when you are skiing.
Have a better stance, parhaps you need to change the position of your bindings. But I think what you need is to ski in a strong position with the center of gravity right above your bindings and not leaning backwards which you most definitely are when your thighs get sore.