Put your girlfriend on a carbohydrate enriched diet, then sit down with your parents and tell them you've "got a problem".
Hey RST, why don't you post nudes of your girlfriend, or even yourself no **** bro in the post your cp thread(since you or your girlfriend would be a child porn), and if you really want you can show your parents, then they'll really believe you bro.
You should follow this trend of dialogue to somewhere wonderful. Fair enough. Divorced parents are so much easier to deal with.