Foot cramps while skiing?

Hello,

I'm a 14-year-old male. For about a year now, I've had a problem when skiing: my feet cramp in my ski boots, and my little toe goes numb. I have flat feet and have only worn rented boots, but have also tried standard insoles. Every time I ski, and even slightly when I run, my feet cramp, and it's almost impossible to enjoy skiing. The cramping is most likely when I'm putting my weight on one foot. Unfortunately, custom-fitted ski boots are too expensive for me.

Hope someone can help me,

Thanks.