Im in so much heartache and pain. please help?

my friend introducted me to this guy about 2 months ago. He was so nice and friendly and handsome. He visited me at school three times just to see me (hes in his first year of college) and i went out with him to the moveis. He also invited me to go with him to a party. So we're talking on the phone and i found out in the midst of all this he has a girlfriend. and he just brought it up casually as if he diddn't care. I really like him and im heartbroken. I thought he really liked me. How can i tell him how i feel? I feel so sad and depressed. Please help