Is carpal tunnel syndrome common in young adults? i'm 19 and experiencing pain in the veins of my hands at night

Depends: Carpal tunnel syndrome is often due to repetitive motions at the wrist due to things like typing; if you are either genetically inclined or have specific activities which stress the wrist area constantly then it is possible to have an issue at your age. Best thing to do is to be evaluated by your health care provider to make a diagnostic and treatment plan.

Not terribly: No, carpal tunnel syndrome is not terribly common in young adults, but it is not unheard of either. Patients will usually have numbness into the 1-3 fingers in the hand. Pain in "your veins at night" is not real classic for it either. Consider seeing a hand specialist to discuss likely cause. Be cautious of jumping into getting a nerve test as there can be many incidental false positives.