Poor lass, do whatever you can, when you can, your strength may come over time.
It really does take time to acclimatize to a changing relationship, this is what's happening, you cannot turn back time but you cannot ignor how this has affected you.
Your mind and body will react when it's ready, whether that is to accept him with his flaws or to try to move on, you are still very young and should not close off oppotunities to make new friends, male or female.
Make yourself the central person, not him, learn to detatch and place yourself first, it's time.
Too many women put men before themselves, yes they think it keeps the relationship connected and alive but in many cases the men are too selfish to appreciate this, your partner is one of those who takes other people for granted.
Learn to stand tall on your own, you don't need a man to hold your hand through this life, you will be ok.