When is it Considered Cheating?

Hey all


 this is my first blog, so bear with me!
ok here's the thing, me and my best friend for two years have always had great chemistry. he was there for me whenever i needed him , and i was always there for him.. one day he kissed me, and it sent shivers down my spine, at the time he had just started seeing a girl whom he had already ruled out any future with.. i didnt want to be the other girl, so a couple of days later i told him "if u want to be kissing me, im going to have to be the only girl ure gonna kiss" he immediately told me he had already cut contact with the other girl, which proved true considering she contacted me trying to find out if I, his best friend, knew what went wrong with them (a little aukward huh).. 

ok, fast forward a few months, weve been together and ive never been happier, although i did ask him to keep us a secret from most people, hes been patient witht the whole situation and everything comes easy with him.. there is no such thing as a completely blissful relationship, so we do have the occasional bump in the road. it makes me sad when i think back to realise that every bump, stems from one thing, jelousy. its completely on my part, ive known him for years, i know his track record, and as long as weve been friends, he never was able to be in a serious long term relationship, i always considered him to be a player. he never cheated on his girlfriends but he did "talk" to other girls when he was with them.

now, in our relationship, he HAS changed his player attitude, but i do worry about random girls i see on his social networking websites, and the online flirting that goes on there. ive confronted him whenever i saw anything that bothered me and his only response is "baby, i will delete them as friends, they mean nothing to me. its completely harmless and they only take it to that level because they think im single, because YOU wont let us go public". then he cracks jokes about how im possessive...

i dont want to be the crazy, jelous girlfriend. he claims that these girls are "just friends" but so were him and I, until we werent.... 

-- so my question here is, am i out of line to be upset that he has all these girls in his "social" circle?