I was born with a chd, double inlet left ventricle, i moved from ny to louisiana 3 years ago and picked up habits like smoking and eating less healthy, long story short, i stopped smoking a few days ago and i'm starting to have chest pains, why?

Likely heartburn. Nicotine relaxes the muscle holding the swallow tube closed to the stomach. That increases chances of acid reflux/heartburn. Once reflux starts, it is a self perpetuating problem. Best to have your doc sort it out. The CDH may/may not play a role, but common things happen to all comers.

Maintain a healthy lifestyle including diet and please follow up with your Pediatrician. A Cardiology referral may be helpful. Chest pain has many causes, and an evaluation is recommended. Watch for signs of shortness of breath, dizziness and cough.