Having sex with a man doesn't make him yours. You had feelings for your friend. Even though he was involved with another woman, you had sex with him. Now you are mad because it didn't work. If you try this tactic again, the result will be the same.
Love comes first.
When two people feel they share something they do not share with anyone else, then they have the basis for the deepest relationship two can ever have. Sex doesn't get you that connection. You've known this man for seven years. You had an airtight friendship. Even sex couldn't make him more than a friend.