Casein protein/bloating?

Here recently, I have been feeling VERY bloated and really full all the time. Prior to the past week or two, I was coming off of a plateau and losing weight steadily. I've recently gone back up about 4 pounds to my previous weight. I know the weight gain isn't from a gain in actual fat, but it's still discouraging to see the number go back up, plus not looking as lean. the weight gain and bloating started recently after consuming casein protein so I was wondering if that may be the cause. Here is a sample of what I've been eating:

Meal 1: 1/2 cup rolled oats, 1 scoop casein, 1 banana
Meal 2: Larabar
Meal 3: Black bean and quinoa vegetarian chili or a turkey/hummus wrap with carrots or small apple as a side
Meal 4: About 4-5 oz grilled chicken breast with a cup of steamed veggies
Meal 5: 1 cup greek yogurt with berries

I like to eat oatmeal & casein in the mornings because I work and like to have something that keeps me full for a long time. Before I started the casein powder, my meals were like this (and I had almost no bloating and lost weight steadily):

Meal 1: 1/2 cup rolled oats, 1/2 cup egg whites, 1 banana
Meal 2: Quest bar
Meal 3: 2 slices of ezekiel bread with a spinach/tomato omelette
Meal 4: Grilled chicken breast and 1 cup of steamed veggies
Meal 5: 1 cup greek yogurt with berries

Do you think I'm reacting badly to the casein powder or is it normal to have this much bloating after using it? Nothing has changed about my workouts, I still work hard. Feel free to make suggestions and offer constructive criticism. All I want is improvement and fat loss, so any suggestions would be appreciated.