Where is the exact location of the pain?
What does the pain feel like? sticking, stabbing, ache, etc.
How long does it last?
How many times a day do you get it?
Do you have any health problems?
It is always safest to have chest pain evaluated by the doctor. This sounds very much like gas pains, especially since they come and go. When you lie in bed, be on your left side to encourage passage of gas. Are you having normal bowel movements? Why do you think you gained the weight? You do have to be very aware of your high stress and find ways to reduce it, because it will have an effect on your body.
I am glad to hear that you are going to have a physical done because the doctor will do an electrocardiogram to see if there are any cardiac changes. This is a good time for you to focus on being healthy. Be careful with your daily menus. Reduce fat and increase fiber. Drink plenty of water. You don't have to do a rigorous exercise program, but try to get back into exercise.
Please let me know when you schedule your visit with the doctor.
Thank you and please keep me updated after your doctor visit. It is free to reply.