Need Advise...

Could you be a little lactose intolerant? I know the syntrax protein powders are lactose/gluten/aspartame free? I use almond milk because I became slightly lactose intolerant. (milk and cream anyway...yogurt and cheese are okay...) Good Luck!

I'm a year post-op, and I find the Premier Protein RTDs to feel more "filling" than my go-to powdered protein.  I suspect it's because my powdered protein is 100% whey protein isolate, and the Premier RTDs aren't.  And the protein concentrate is higher in lactose (do you have trouble with other dairy?)  and cholesterol.
I still like them for convenience when traveling, or when I'm on my way out the door for a hike, and I think it's not a bad thing that they give me more of a "full" feeling, but I definitely have to drink them more slowly, and often I don't finish the whole thing.   You might have an easier time with a product that's based on whey protein isolate.  Also, isolate is easier for your body to digest, which can be especially  important for an early post-op. 
In the early months, though, your tummy is still really swollen, so anything can give you that bloated, stomach-ache feeling if you try to get down too much too fast.  1 oz every 15 minutes for starters.

 I think that is what's happening to me...they really do fill me up.  I tried Isopure drink (like kool aide) and it was not good.  I'm going to my Support Group on Tuesday and hope to buy something else then.  I have to!  I just didn't think it would be this hard to find something I like.  I'm a foodie for heaven's sake. I've not had any trouble with other dairy. Today, I tried to space it out during the day, but still couldn't fini**** all.  Thanks for responding:)