Please give me advice, I think I've been a bit silly, now i dont know what to do......?

Girl meets boy, and its instantly an attraction. I mean instant. Phone numbers are exchanged, and the deal is cememted that night. Then after a few mad nights of absolute passion, we finally leave the house. we get on well. its going good. we understand one another intimately, and intellectually. oK good. then he says we are getting attached ... uh oh. i cant get attached we are both from two very very different worlds. so i tell him, that i cant end up with him long term, but would love to share his company while i can, after all, this happened fopr a reason ..... he's in two minds, and then tells me that he knows, that now, he is truly on his own in life ..... huh where did that come from im thinking to myself.. ... .. ermmmm what to do now ....... so i say babe, we get on lets have a good time, and enjoy each others company ...... but i say if he wants to be just friends that is cool, he thinks about it for a second, kisses me passionately, and then after about half an hour, he leaves. ....in the past, he has told me that he doesnt see lots of girls, and has never been like that. .... then in the last few days, i have seen him with two other chicks, and last nite, we were together where he works, after spending most of the weekend together,,,,,, this girl walks in, he tells me theres kind of something going on, and he asked me to leave. i say ru serious ..... he says yes .... puts his head down, turns round and walks away, leaving me to justg go .......... i obv dont wana see this stuff, what is he doing ..... and what do i say to him please please gents, help me figure this one out. cheers. xxxxx