I can’t leave him

Do u ever just feel like ur in too deep with someone? Like I’ve been with my bf over year and he’s been my first everything. First real relationship, first time having sex, first love. It’s like even if I rlly wanted to leave him I just can’t because he was my first, I feel so attached. (I’m 17 and he’s 18 btw) some days I’ve thought about leaving him because i worry we’re not right for each other but then other days I’m my happiest with him. I just don’t feel capable of breaking up with him. I honestly don’t think I can live without him. I’ve suffered from suicidal thoughts before and he’s the only reason I’m still here. He gives me a reason to stay living🤦🏻‍♀️ I hate being so attached but I don’t know what to do. Is it a bad thing?