The chest pains are most definitely gas. Do you feel them in your back as well? Especially in your left shoulder blade (apparently there is some nerve that's connected from your stomach to your shoulder blade - the things we discover)... For me, the gas pain lasted 2+ weeks. To be honest, I was miserable after surgery and had many regrets, especially in the 1st week.
You lost a lot during the pre-op phase! That is amazing - Congrats! Follow your plan, don't eat pureed and solid foods before it is time, and most definitely focus on your protein since it helps with your energy levels. Also, don't be like me and think that you can clean your whole house a week post op and not feel any pain. Don't lift more than recommended, and take it easy. This whole new you has just begun, and you are on an amazing journey. Enjoy the results!