I don't know what to do. i don't wanna hurt him?

ok i just started dating this guy about a month ago. yea hes really sweets and a good boyfriend. but heres the problem when i went up to stay wt my cus for a weekend i met this other guy and i lke him more. plus the guy im with now is getting attached WAY to fast saying im the best thing that ever happened to him... i told him i was moving to colorado and i dont want him to fall for me any more than he already has and he wont stop i dont wanna hurt him and i dont know wat to do?? someone plz help me