I Had A Reversed Colostomy Bag Over 3 Year Ago,

I had a reversed colostomy bag over 3 year ago, been off and on chemo for 3 yrs i'm off chemo now and I have very bad gas pains in my lower abdomen and lower back every night how can I avoid this or what should i take to help this out, I have to walk the halls for hours for like 3 hrs and then it finally goes away and i fall asleep...