Chest pain and back pain is this caused by gastritis

I was dignosed with gastritis and acid reflux about 7 years ago it went away after 1 year or so I lost 50 pounds stopped smoking drinking. Just about over 1 Month ago the chest and back pain started it scared me to death I thought I had lung cancer. I went to the ER because i couldnt bare the pain anymore. The doctor told me I had poop backed up in my stomach this was causing the chest pain and back pain they took xrays of my chest my lungs are fine. After going to see my doctor she tells me its stress and anxiety and today I still have the pain. I don't know what to do now do I believe the doctors or what. I still think there is something wrong with me besides anxiety does stress and anxiety really cause this much back and chest pain. I have no joy in my life what so ever because of this pain. I am a Chrsitian and a true believer and have been praying day and night for healing im still waiting just real frustrated and advise out there please.