My boyfriend seems to think his happiness is based solely on me/our relationship

Bit of a background my boyfriend and I were friends for a long time before we started dating, and he’s always had issues with his mental health. Once we started dating/got more serious he started telling me how happy I make him and like I’m the best thing in his life, I just worry he’s ignoring his problems because he’s content dating me or I’m less of a person to him and more of a “fix all my problems” sort of deal, how do I go about bringing this up to him without sounding like I’m projecting.