Marriage falling apart .?

My wife left me for the second time . The first time we were together for 6 months not being married and relationship i thought was great . But she started acting different with me and then the day came when she sat me down and said its not working she needs her space she fells like we have fallen into routine so i kinda expected something which i was right she left me for a coworker man that destroyed me and i didn't know what to do . So i just found a place and moved . After everything happened she wanted to talk to me so we went to starbucks and she told me everything that she wanted to end things because she did not want to cheat on me . So i was starting over again and she would call from time to time to come over and every time she came we had and things seem like she made a mistake so 2 to 3 weeks went bye and slowly she started staying with me more and more each until she moved in . I tried to put past that she slept with another man but i don't think i did . So everything seemed Fine we went to new york i asked her to marry me and for several weeks everything seemed ok until last week from one day to the next she started acting diffrent with me .Then yesterday she laid the bomb on me again but this one was atomic. She needed her space this time that there was no one involved and that she is not happy with her self and that she wants no more obligation she just wants to focus on school and she cant keep acting fake like everything is ok . I was in shock because i have giving her everything she wanted and i have supported her school and been there for her from her first divorce. I really dont know what to do and how to save this marriage .I love her to pieces and something inside of me won't let go .She is a wonderfull woman at times and yes she is controlling at times but everyone has flaws .I also know this is not healthy for me and i know i cant continue to live like this but i want to try one more time . What do i do how can i approach her in away that doesn't make me desperate or should i just give her her space and completely distance myself from her like i should of the first time and just focus on me . HELP!!!