This idea of changing yourself to be who you think people want is pretty exhausting for you, and ends up being disappointing for all involved. We can only fake who we are, fake what we like and don't, and present a personality or behavior which isn't true to our core for so long.
The results of this is not good. People will eventually stop faking and when they do they are often surprised that the friendship or relationship fails. The mindset goes back to "shouldn't you like me for who I am"? Insecurity and resentment grows. In the end the person who faked it loses anyway they put on a mask to be what they think someone else wants so they can assure a relationship - then when they remove it are shocked to lose the relationship (be it a friendship or romantic interest).
Your most recent events prove this. You told the dude what he wanted to hear, you did what you thought he wanted, then you freaked out. Of course you freaked out because you aren't ready for a relationship. Then he bolted for the hills, not because there is something intrinsically wrong with who you are, but because you waved the flag trying to back step, then tried to change that, then change again. All actions trying to find the one that would work to get him to return to "liking" you and act like he did in the first place. In the end you ended up rejected which is what you were trying to avoid in the first place.
I don't know how to tell you to get to a place where you just be. To me I say be yourself - its not YOU, its your behavior. Behavior can be changed. The ironic thing is this person was attracted to the real you, its the fake you that contorted to offer him what you think he wanted that was rejected.
I hope you see this. Rejection is an unfortunate part of life (or as I have realized can actually be fortunate. Some people aren't meant to be in our lives, and aren't positive for us).Not everyone is going to like us. That is ok - Do you like everyone you have ever met? I doubt it.