What to Do?

I am having difficulty getting over my ex. When we met we fell in love instantly and and spent every day together. I never felt this way about anyone before, not even my ex-wife ( I married very young) at any point in that relationship. We were engaged within four months of meeting and lived together happily until a month ago( minus a few BIG fights and not much intamacy the last year). I am the only father her young daughter knows and this makes it even worse. My ex fiance's reason for the split is that she cannot tolerate my ex-wife, which is only around when we exchange my five year old daughter, but I really think that she does not like my daughter although they used to get along great. Also, I met her soon after leaving the military but now I am going to return to the military and she says she doesn't want that life. I work full time and go to college full time as I have for the two years we have been together and I know that is hard on her but I have taken care of her a couple times when she was out of work but  she never seemed to appreciate it or my efforts to better our lives, and she has no desire to obtain a better means for increasing our quality of life herself. She is content being uneducated and working low skill jobs for poor wages. When she left she moved in with her mom and step dad so that she can spend her money and not pay any bills.

She told me she wanted to stay friends but still wants a sexual relationship with me and I said ok. Not long after I heard rumors she was dating another guy and I lost my temper. I heard this at work and went so far as to throw my keys ( I am a manager) at my boss and storm out. Fortunately he is a good friend and talked me out of it and acted as if it never happened once I calmed down (an hour later) and I returned to a logical state of mind. She told me the guy was just a friend (still not sure) and a few days later she told me he sent her a text at 1 a.m. wanting her to come over and do sexual things so she no longer speaks to him. Maybe she wasn't lying since she told me, I don't know, and every time I saw her she was wearing my engagment ring even when she didn't know I would be seeing her (at work). Anyway, I came to the decision after this that I could not be friends with her because I don't want to do something stupid because I find out she is seeing someone else, so I tell her this and let her know if we aren't together we must severe ties. She then wants me back! She says she can't lose me forever and she is willing to give military life a shot. So we get back together, but only as being together and not engaged. It is weird. We spent a great night together away from kids in a hotel suite and the connection (and sex) was better than ever. My problem is that everything doesn't seem to be adding up and I am wondering if she is only with me because I forced and all or nothing decision. Not long after the breakup she said she loves me but is not "in love" with me and doesn't know if we will ever again be more than just friends. Now she says she loves me everytime we speak and the night we spent together she said I am again like the old me she fell in love with. I am so confused. Am I being played? Is she confused? Is she holding on to me incase she realizes she made a mistake? I am 25 and she's 21 so we are young and I understand that but I love this girl but should I just move on now or give her the benifit of the doubt? I am prior service air force but I am enlisting in the Navy under the SEAL Challenge contract because I wanted to be a SEAL since I was 15. This is the toughest training in the military and requires full focus and determination to succeed and I fear while I am in training she will break up with me again and put me in a tougher situation, or I will worry she has found someone else while I am gone. I don't know what to do.