HE is afraid that he will disappoint you in some way or is not ready for a commitment with you.
I agree with the disappointing part. I have said this to women before because I always felt that I would disappoint them and my track record kind of proves my point.
In some ways, it is a plea for sympathy to him to draw attention to poor little o'l him...in other ways, it might indicate he is wanting to play the field but not hurt you, or that he just doesn't know what he wants. He may very well like you but not be ready to be with you at this time. Life is so short, and it's truly to your advantage to find someone who enjoys your company, likes and respects you for who you are and who isn't looking to be the main event of your relationship. If someone is concentrating on his woes vs. developing something special, he is merely making you an option but certainly not a priority. Chin up and look to higher grounds for a more fulfilling and enjoyable relationship. :)
He needs time and he thinks he's not ready for a relationship.
If he's the kind of guy who can be very thoughtful, shy, ... Then chances are that he has a low self-esteem and that he considers you out of his league and that he doesn't deserve you.
Other than that, he might be telling you in a polite way that it's best to stay friends for the time being.
All I can say is that time will tell ...
he has no or little confidence...he feels he has nothing going for him...
If it was up for discussion, you should have asked why. Hit him up again.
He has LOW SELF ESTEEM.
There is a problem?