I did not have the same surgery as you, and I don't know much about banding, but I had extensive rectal surgery a month ago and can only offer a little advice based on what happened to me. I think it is normal to feel heaviness and pressure after such a procedure. I also felt the same "pressure". Unfortunately, I didn't listen to it, and ended up impacted 3 times after my surgery. That was aweful!
If your not on a fiber supplement, I would recommend one, and don't go too long before trying to pass stool. For me, even still a month later from my surgery, I have to prepare myself to "push through the pain" to have a bowel movement. It has gotten so much better, and now I can tell if I am starting to get plugged up a little, and am careful about what I eat. There is a very fine line between pushing through the soreness to have a bm, and straining too hard and hurting yourself and doing more damage. I would try to stay as regular as you were before having the procedure. If you are worried, Milk of magnesia 1 tbsp is a very gentle way of helpng things along. I used it the 3 times I was impacted (never more than 2 doses) Also increase your water intake a lot!! (100 oz per day) Raisen bran helped me out a lot also. Hope your feeling better soon.