Unhappy in a relationship

I (19F) have been with my boyfriend (21M) for over 4 months now and I just don’t see a future for us. We jumped into our relationship fairly quickly, his past relationships tell me that this is common for him. He’s young and his 2 serious relationships only lasted 2 and 5 months whereas his high-school romance lasted a year and a half. He told me he loved me right away and I told him I felt the same although I knew in my heart then that I didn’t feel that way and I still don’t. We just don’t have many similar interests and he seems to have his own opinions and doesn’t hear mine out. We haven’t fought much, but I’ve wanted to, I’ve wanted to give him a reason to end things. I’m scared if I broke things off I’ll seem like a monster, my family consider me a man eater for some reason even though I’ve never had a proper relationship before this. I am unhappy though, my mental health has declined rapidly since the beginning of the relationship, I’m struggling with so many things. I can’t sleep, I’m tidying constantly but not taking care of myself, I barely leave the house. I’m just overwhelmed, this isn’t what I want or need right now but I don’t know how to tell him. If we break up I know we wouldn’t remain friends, that’s not his thing and I’m glad. I just wish I hadn’t rushed this, there’s been too much too soon. I want the old me back.
TLDR: Unhappy in my 4 month relationship, I want the old me back.