I had read your query the day it was posted but I wanted to write neatly.
You are not alone and neither the only guy who is going through this phase. There are lot of guys who gets ditched by their gf after 5+ years, while for girls its other way round, if they were to get ditched, they are ditched within 3-4 years max.
I agree with Sourav, no matter how much a woman claim, she is indeed emotionally very weak and unstable weather career oriented or relationship oriented,they cannot support,that's my experience as well.Must have noticed bad boys with 5-6 fr and nice guys having none and then they whine about boys when they choose to side with bad ones as the power of choice is in their hand.it's only in words that they want funny, caring and loving guys but once you notice all girls who actually live guys for real are the guys who are exact opposite of what they want.May be she loved you, but trust me she no more loves you or is even interested in you. She isn't attracted to you anymore. Reason is that, with time she got assurance that she can take you for granted which killed her thrill of relation. She can predict eveything you would do in all different circumstances. You doesn't give her any element of surprise. You are open book to her whom she knows what is written on which page. She knows how will you react to her actions, how will you convince her, how will you treat her. There is nothing left any new element of surprise in you from her perspective.even the surprise gifts you gonna give is known to her that you gonna surprise her now.Attraction is an important aspect for which one gets into relation and which keep its going. So over the period, technically she is bored with you. Beside she isn't seeing anything great happening in your life in future like you going to become some legendary person or gonna become a millionaire.
Girls are not driven by emotions only. It's their estrogen cycle which give them identity among human and their emotions.History has been an example of girls ditching guys for more successful person. That's why it is advised to give relationship the name when you know you have met the one because over the period that the one too gets drifted.Women are very competitive among themselves. From makeup to dresses to bf. They compete and the opinion of their girl gang is very very important to her. If couple of people tell her that you doesn't suit her, trust me she will almost get into doubt whether you are right for her or not.
She may have soft corner for you and will be there for rest of her life but trust me, you are not in her love life anymore until you do something remarkable in your life. I have seen may examples as such in real life around me. There are also other factors like she must have come in contact with some other guy who is more interest in to you, or may the newness of that guy brought into her life is enough for her to ditch you.
In this time you will feel broken, rejected, left out, played with which will lead you to think that there is something wrong with you and this will hammer your self confidence to a new low. You will cry, crib, plead etc.. But she isn't gonna come back. Even if she says she is coming, there are very bright chances she will run away with in a quarter year. The more you crib and plead the more she will think her decision is right and will make her feel superior beside loosing respect for you. And its not gonna help but you will hit the lowest point of life from where few come back stronger but most are ruined forever.
My advice to you is accept that you too don't need her. After all the things she has done, though you love or loved her, stop cribbing and pleading or asking her to come back. Save your self confidence. Trust me even I she come back you ain't gonna have that much faith in her as once if she can leave she can do it twice and over. Try to get stronger. Use other medium, your friends to get through this phase. Drown yourself in work and grief as long and as much as you want. But don't contact her or plead her. May be someday if you could keep your respect in her intact, you may become friends but right now break all contact. If just seeing her makes you weak. Block her from all social circle but don't forget to unblock her whenever you get back up in life to let her know you are just fine without her. Just man up dude. People die in war, accidents etc you just had a heart break. And once you get over the grief period improve yourself and your persona. Then start meeting people with new energy. But only after you get over her not in a rebound.
Stay strong man. These days too shall pass. Jusy hold on. And forgive her. She only deserved your pity and forgiveness not love. Save it for your mom and the woman to come in life.