A 17 year old likes me. What should I do?

[Ross]

I'm a fourteen year-old boy, bisexual, and a seventeen year old boy from America likes me.
So I liked his page on Facebook and he added me as a friend, so I accepted. He started speaking to me on chat starting saying stuff like "you're cute" and then he asked me for my Kik username (app) and I gave him it. And now he talks to me on it everyday. Anyway, he still started saying I was "cute" and started saying really sweet things to me, and one day he asked me if I would go on Skype with him, so I said yes. We just had a general conversation on there for a few hours, and then I had to go because it was getting late (and the time difference) and then after he started talking to me on Kik again and he was saying he would send me Xbox games through the post and I insisted that he wouldn't but he said he is still going to. He is being really sweet and I like him a bit, but I already have a boyfriend and he knows, but I don't want to tell him to stop, and I don't like the idea of the age differences either (Is 14 and 17 an OK age difference?) Anyway, I don't know what to do? Can you help me? How can I tell him that our age difference might be a bad idea? How can I tell him to stop? But no one else has been as sweet as him. Help me? What should I do?