I say find a new partner in life! That one that u left behind wasn't right for you and you will find that Many times in your life! Take this as a life changing experience that you had with him or her and try not to brew over him/her.....find someone else and it will make your life better! When life gives you lemons, make lemonade (or chuck it at a lama! No Jk)!!
I'm sorry you are in a deep emotional pain, I have 2 recommendations, but both require to make time for reading. Find your self a book by Don Miguel Ruiz, the book is called The 4 Agreements. This book will help you understand Love and will teach you how to Love unconditionally. You are Love start by Loving Your self.