Some times though actions don't speak louder than words.
May be in this case he cant expresss to you what he feels perhaps he might hurt you in some way and thats why he cant be with you.
He might have issues you do not know about and thats also why he is ok with others but not with you,because it will hurt you too much knowing and he doesnt want that for you.May be??
How may times do we think we know some one,or something about a person to only later on find out we truly didnt.Thats why we say "dont judge a book by its cover" and some time the first few pages,and the ending isnt always what we think its going to be.<br/May be you should try to write an in depth letter to him,but not throwing it all back on him,just on expressing your feelings and why perhaps he says he loves you but cant commit.See if he responds to it,if not,then you mght just have to forget all this and try your best to move on.