You should get checked out by your doc. In the meantime, if the pain becomes severe, go to the ER, since it could be a bowel obstruction or hernia.
Recently there was a bypass patient that had to get surgery for a Petersen's defect. It is a fairly rare complication of the bypass, and it can happen anytime postop (even 13 years).
Hopefully it's nothing, just some constipation, but better safe than sorry...