I desperately want my growth plates checked, because i'm so curious about my height! doc says its too much radiation so no. is this valid?

No need to check if: If past the teen years, and no height growth happened last year, then growth has finished. There isn't any reason to x-ray growth plates if growth stops at that age. To look taller, one can choose properly designed clothing and shoes, and have good posture. Vitamins, supplements, "special" foods, exercise, etc... will not make a person taller (height is mainly genetic or familial in the US).