My dr started prescribing this to me 3 weeks ago. I've been having these symptoms: upset stomach, gas, constipation, bloated, fullness and not being able to eat much. Can this be from the Codeine? I used to take this 3 years ago and never noticed these side effects before. Also I was on oxycodone 3/325 for last 3 years and had not side effects. If the symptoms are from the codeine, why I didnt I get the same side effects from the oxys?