It looks to me like your girlfriend is afraid of commitment. She gets close to you and then she needs her space. What is her experience has been with other men? Did someone hurt her? After a year and a half you are right I think even if you do not think about marriage most people do and if marriage freaks her out thinking about it will freak her out. You are doing the right thing with giving her space. I would also like to ask if she is depressed because she sounds like she may be. If she wants to be away from everyone sounds like isolation. Has she done this pushing you away and pulling you back in before? Why did the giving her space feel like a break up? What is your own experience with relationships? Did you feel like this before?