I gained weight and I don't know why

I have gained 3 pounds when I weighed myself this week. It has been almost 2 weeks since I lost weight and now this. I am only 4 weeks post op. I am on pureed foods. I drink 3 protein drinks a day made with soy milk. I eat chicken, tuna, ham or shrimp salad at least once a day. I have yogurt(light and fit) for a meal. I have more protein for supper like roast or meatloaf. I aviod carbs because I know I need protein. The only carbs I get are good carbs from cooked carrots or maybe some beans. I exercise at least 30 mintues everyday and take my vitamins. I am doing everything I was told too. I am very upset I can't figure out how I am failing.

You are not failing. Your body is adjusting to the new lifestyle. How much have you lost in inches. Are you getting all your water in? That is important too. Take some measurements. Remmember this is a journey and the these little plateaus are common. Also is it right before your cycle. Some women gain right before the onset of the menses. Sorry to be graphic here. Think about that too. Only weigh yourself once a week. Now just keep working your program