I have several scratch marks on my leg and buttocks . they are red in color and are several cm in length and criss cross each other?

Scratching: I presume that you do have itching at the legs and buttocks and thus the scratch marks. One's skin tends to dry up especially in the Canadian winter. Try apply a moisturizer all over <3 minutes after bathing to see if this helps.

I don't know how old: ...you are or whether you're doing strength training or other athletics, but (unless you've had an injury) most likely what you're seeing are stretch marks. These are defects in collagen formation that can occur during rapid growth. They're very common in pregnant women but often occur in boys/men when they're growing quickly or working out with weights. If concerned, see you doctor.