Colostomy help?

Hello - I was wondering if any of you out there with colostomies might have any hints on avoiding gas pain and constipation? I thought I was doing fine then I woke up Tuesday feeling constipated so I took some Milk of Magnesia. Then the cramps came like crazy. I ended up calling the dr and they had me go in for an XRAY. Which just showed constipation. But the pain was actually unbearable so they admitted me and gave me morphine and Miralax. I was let go today but I never want to get that pain again!! I am thinking more water, prune juice and walking, but wanted to check if you all had any hints?