The answer lies within your ex boyfriend. For some reason, he decided to end the relationship. He chose not to tell you which is one of the problems. He also is using the same expressions of love on his new girlfriend. That is suspicious.The fact that he cut off your relationship, moved on and now will not speak with you at all is very odd.
You are right. A relationship that ends in this way is hurtful and confusing. However, your ex's behavior says a lot. Enough so I suspect that he has some issues you were unaware of such as a mental health problem or some other emotional issue. If you cannot find anything you feel he was reacting to in your relationship with him, a mental health problem or emotional issue are the only things that could cause such a reaction.
Most relationships end with each person at least mostly understanding what happened to break them apart as a couple. Also, most relationships have a process of breaking down. Each person can respond to the break up either by getting help or responding another way.
It is ok for you to feel the way you do. It was a shock and it was unexpected. You may be in mourning over the relationship as well. Give yourself time. Gain support through trusted family and friends. Go out, pamper yourself. Your self esteem is low from this and you can get a boost by treating yourself well.
If you find that after a few months you still feel this way, see a counselor. Your doctor can refer you or if you attend church, your pastor can help. You probably only need short term therapy just to help you cope.
Here is a book that may help you. It's called Coming Apart: Why Relationships End and How to Live Through the Ending of Yours by Daphne Rose Kingma. Amazon.com has it available or your local library may have a copy.
I hope this has helped you,