I need advice on my 3 yr on and off relationship?

Basically, I've been on and off with my boyfriend for the duration of our three yr long relationship. What I need advice on exactly, is for myself. I keep running from the relationship but when i find myself outside of it i miss him so much and i want him back. We've done the just friends thing but it usually turns back into a relationship because we both are pretty awesome people and we do well together. I dont know why i keep getting cold feet, i guess mainly its because i could see us going the distance. But my subconscious keeps bringing up stupid reasons for me to run away, like vanity reasons like i could find someone maybe thats cuter, or because he has lost his job and his car is broken down and its been a year since he's been able to land anything solid to make enough money to fix his truck. And then there is the slightly bigger issues, i cant take criticism well and on the occasion that he does it makes me cry and i take offense to it, and that ends up annoying him and he'll get angry over me crying and telling me i need to grow up a little bit more. When we are good tho we are really good. A lot of these issues have stemmed from me feeling like i fell out of love with him, even tho i still love him as a person. When i think about a future with him, we are very compatible. I dont know why i am so afraid to commit. Any advice on what to do? Right now I am broken up with him because its not fair for him to be in a relationship that is so indecisive. He loves me a lot, and i know he wants me to be "the one", and we have a great bond together. Please help. I am too shallow of a person and too indecisive, and I do believe i have a lot of growing up to do still and i feel like that THE problem.