My wife became so interested in my diabetes, that I often say to friends that she has taken over my diabetes. Every so often I had to remind her that it is my diabetes, not hers. She often reminded me about times to measure, what I am allowed to eat, and what is forbidden. I say that I can eat anything, but to keep in mind how it may disturbe the values. I became upset when she suggested that it was time to go biking in order to get my bloodsugar down, and I resisted many good advices because they came from anybody but myself.
We made a joking about this, and she understood that the best way to cooperate about my diabetes, is that she shows interest and gives a helping hand. So we are planning our meals and exercises together, and if I don't remember to measure before a meal, it's not a disaster. I can do it next time. Maybe easier for us with type 2.
It seems to me that your boyfriend feels that you a little overwhelmingly have taken over his diabetes, and that he has lost some of his ownership to his own disease.