Help

I am new to this and need some serious advice because I feel like I am completely losing my mind.
I have been in a realtionship with a man for about 10 months and within the 10 months this man has moved into my house (and doesn't pay a dime) proposed to me and wants me to be a step mom to his 2 children. With all that being said he has complete control over everything I do. I feel like I walk on egg shells daily. I don't know what person he will be from day to day. One day things are so very good and the next day he is making accuasations about me cheating on him with any and EVERY person I come in contact with. He has isolated me from all my friends and family. ANYTIME we go out of the house he says that I stare at other men to get attention. He has accused me of false relationships with co-workers. He questions everything I do as if I have hidden agendas to cheat on him.
I have NEVER cheated on him. I tell him everywhere I go and have even taken pictures of places that I am at to prove to him I am telling the truth. On the good days he is nice to me and will talk to me and carry on conversations and really act like he cares about me. That is what keeps me in the relationship. On the bad days, when I try to communicate with him he accuses me of everything under the sun or will ignore me or walk away from me or not answer phone calls. He has made me apologize to people because he said that I wronged them and I am constantly apologizing to him for things that I don't even understand what i've done wrong. He truly makes me feel like I am worthless and that I am going crazy but because I am always trying to prove to him how much I love him and how true I am to him.
When he starts fights I beg and plead with him not to leave me. Its almost like he has me believing the things he makes up in his head. I don't understand it. I honestly give this man everything I have. I did get upset one time and kicked him out (after he didn't come home one night) and he made me feel so bad and said he couldn't believe I did that to him and how can I let his kids see him like this etc (because he had no place to live-but a hotel) I let him move back in with me 3 weeks later. He bad mouthed me to everyone in his life and they all think that I am a horrible person and that he is a great man.
I don't know what is wrong with me why I continue to let myself go through this abuse. It is absolutely killing me inside. I feel like I have to live a double life because I am so ashamed of my "home life" that at my work place I put on a huge "front" because I don't want anyone to know how weak of an individual I have become.
Please any words of wisdom. Is this typical narcissitic behavior this man is displaying and am I a weak person? Thank you!