I have been taking Nexium and Tums a lot for the past 3-4 months. Ever since my GERD became really bad, my stool has been light brown colored or yellow colored sometimes bright yellow. It also came out green last week. I forgot to mention this to my GI Specialist. I'm 27 years old. I also experience a lot of lower middle chest pain too. The nexium used to help the chest pain but not anymore. Any ideas?