One thing that comes to mind when I’m hearing about your story is that you are essentially making this woman the center of your universe and instead of focusing on your goals and your purpose in life, you’re thinking about how to please her. she’s preoccupying all of your thoughts and all of your desires and you were thinking about her instead of to yourself you’re thinking about what she wants instead of what you want you’re thinking about and moving your life around how to make things convenient for her rather than Thinking about how does this relationship serve goals and my aspirations for life, professional life or prodigy and continuing your bloodline. 

When a woman can see that she’s the center of your world it gives her great anxiety. It increases her anxiety because she already lives in an uncertain and volatile emotional world that is full of ups and downs and uncertainty. her biology makes her weak and unable to defend herself, even bleeding once a month during her menstrual cycles. On top of all of that, if she were to bare your child, she would be helpless and unable to defend herself or provide for herself for a year plus with pregnancy and caring for an infant child. Because of that she’s looking for a man who is superior to her and all respects and is concerned with his own strength, well-being and Direction in life. She’s looking for that because that’s what she is naturally attracted to. 
Often times women will say things that are not necessarily aligned with what her actions actually show. For instance, she might say that she loved it that you said you wanted to marry her after three months, but in reality that may signal weakness and neediness on your side showing that she was your best option, and thus hypergamy was not satisfied. Hypergamy is simply the fact that women are going to be attracted to men who are of a higher sexual market value than them.  That means that a woman is going to be most attracted to a man who she knows is desired by women who are as attractive or more attractive than her.
I think that what you’re dealing with is very common in this day and age and Im engaged with helping guys like you get this area of their life handled. If we dont properly generate attraction and genuine desire in the women we are with, they will cheat, leave, or poison drip the relationship. 
Happy to chat more if you’re interested.