What's wrong with me?

My boyfriend who I've been with for 2.5 years is the man I've always said I wanted. He's faithful, loving, has taken my daughter in as his own. He's wonderful. Why am I on the verge of breaking up with him? I don't know what's wrong with me. He is everything I ever hoped for in a partner, but yet I feel like I need to leave.. idk what's wrong with me or what to do.