Getting protein

I am having this issue where I can’t gain any weight. I’ve maintained same weight for like two exact years now. Not that I’m complaining, but everyone says they gain weight when taking insulin. I just don’t see it. I even started drinking protein shakes ( premier protein, fair life and muscle milk). All of these say 5g sugar, but might as well be 50. My sugar was 126 and I drank a single bottle of premier protein and my sugar escalated to about 190. It’s settled now, but anyone else run into these problems with protein shakes? I’ve been searching and it looks like BOOST is a brand meant for people like us.