DESPERATELY need advice😭

My boyfriend and I have been on and off for 6 years. People say I'm stupid for going back so many times but he was my first true love and he's definitely my best friend and he's always there for me. We're together right now, but we go through spells where it's perfectly fine and then it's like he flips a switch. He's told me that he doesn't care about our relationship but the only reason he stays is because he knows he'll be miserable without me. And then it's like he flips the switch back on and he apologized and says he hates that he says stuff like that. I am in love with him but I hate constantly worrying about what version of him I'm going to see. How do I make it stop?