Dana,
Thanks so much for checking back and giving us the update. Your dad is sure lucky to have you around to do this for him (I take it he isn't the one to spend his free time at the computer). I only let my daughter post for me for the first few days after surgery. Then I took it over again. . .
As the others have said, it is possible for dad to be retaining fluids - even now, months after surgery. I had some fluid retention for a couple of months after surgery, and took some heavy-duty diuretics to get rid of the fluids. As time went on, it became less and less of an issue. It can be bad, though, if it gets to be too much before dad sees the doc. He should do that, pronto.
Also, as I've learned, some of the other meds they give us can have side effects. Beta blockers are my nemesis. After surgery they had me on a heavy dose, due to trouble regulating my heart rate. Over the (almost) 2 years since surgery, we have cut the dosage in half twice - started at 100 mg/day, now 25 mg/day. I feel MUCH better. Part of that is the continuation of the healing process and part is the impact of less meds.
As for your dad's "digestive" issues due to the pain meds, I had it to the max. Mine was so bad that 4 weeks after surgery I was re-admitted to the hospital to get help in dealing with it. It took some industrial-strength meds to get things under control and I think I still have some related issues. I would advise dad to have a good talk with his cardio about this, too, if he has any lingering issues.
Do stay in touch. We like to keep track of the "family."