What should I do !?!?

Okay so ive been with my boyfriend for almost a year now & the past few months (5 months or so) he’s had a sign of psychosis . He talks to himself , laughs , & says all kinds of crazy stuff as “I have another soul in my body” etc . Off the wall shit . How can I convince him into seeking help ? He knows theres something wrong with him . I don’t want to leave him because for one I truly love him & im not ready to let go yet . & I don’t want to leave him by himself . Does anyone know how I can talk to him about seeking help ? Or just an advice ...