When you don't have that trust in a relationship, you have nothing. She couldn't be honest with you for a multitude of reasons I'm sure (Do you overreact or hound her about everything she does? Does she feel comfortable talking to you about anything?). The relationship was destined to fail as tough as it is to realize that you were blind to it for years and years.
What did you learn about yourself from this? I know you want to beat yourself up but she contributed as well. You gotta dive in and see all the things that went wrong and who was responsible and what you could have done instead. This is the only way you will be better from this experience.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.