agreed with >>16 here, don't do it over messenger, you really need to see him face to face and read expression/body language. Also as a rule never do break ups or ask ppl out over messenger because it gives the impression that you're hiding behind a monitor because you're afraid to actually be close to someone, and also that you might be insincere. Oh and as a sidenote, its much harder to say no to someone face to face rather than typing "n-o-." on keyboard.
Oh and i'd suggest you dont say stuff like "im begging you" and "please" and "dont reject me" ect. because that makes you look clingy and nothing drives a guy away faster than that. From my limited dating experience, thats a bad way to start off. Something closer to "i really enjoy your company and would like to further develop what we have" might sound more mature and on an equal scale. Really how you approach the guy depends also on his personality, and since us anonymous ppl on the internets haven't met him, and will never know him as well as you do, you're the best judge on how to approach him.
Since you breached the subject over IM, hes responding with 1-2 word answers, and obviously dodging the question like a politician. You kinda dropped a HUGE hint on you're motives, if i were in his shoes, these thoughts would cross my mind. 1) I dont know what to do, this hasn't happened to me before <think deer under headlights frozen in front of car> 2) i'm hesitant to hope for much, maybe shes just using me to fish for responses for when she asks another guy out 3) i'm afraid of answering in affirmation because if im mistaken i'm gonna look real bad and be really embarrassed. 4) why is she acting weird all of a sudden? is this a manipulation move? and for what?
Like the conventional wisdom says, integrity is the best path to take. So fix a time 1 on 1 with him over a cup of coffee or something, and tell him straight what the deal is, instead of sidestepping and hinting. if he really is dense, he will value your frankness and honesty. Its like when you train birds, you always approach them from the front where they can see you, if you sneak up behind them then they get startled and fly away.
oh and do fix the spelling please, it makes it easier to read and to take you seriously. I doubt you'd be taking my advice into consideration were i to 7YP3 !N 1337 H4X0R SP34K!!1oneoneshift-one