Dating blues

I've been with my boyfriend for 3.5 years. And I love him as a person and best friend but I just randomly get really annoyed with him. And sex is mediocre. But I know I'm not in love with him anymore. But I still love him and care about him. And idk if this is normal. We live together but we're not engaged or anything. But I'm not sure if I should stay with him cause I'm almost positive he is not the one I am meant to be with but I really do care about him. So idk if I should just stick it out cause we do work well together as a couple and what if I do let go of him and realize that I don't want to lose him after all? Has anyone been in the same situation and if so how did you deal with it? (We're both 22.)