Yikes Pam, that sounds serious. It could be a stricture in the intestine, or a blockage from the surgery healing and intestines stuck together or something. He needs attention ASAP, have you tried contacting his doctor and telling them there is an emergency? This soon out of surgery it would not be unheard of as the complications usually appear early if they're going to appear at all.
I hope you get can him to the ER or his doctor very soon. Usually extreme pain makes those who are usually stoic quite amenable to intervention, sorry to hear your father's being so stubborn. it doesn't make it easier for the caregiver either.
Please let us know what happens.
Wendy