Flirting can mean many things, and only one of them is "feelings".
Guys flirt because they are testing to see if you give out free sex.
Guys flirt because they are bored and flirting is fun.
Guys flirt because they are insecure, and flirting makes them feel desirable and manly.
Guys flirt with one girl because they want to make another girl jealous.
There is ONLY one definite indication that a guy is interested in you, and that is if he asks you out on a date. Of course, it may only be sex he wants, and he may not be interested in anything other than your body.
But if he is still dating you 6 months later, then there is a good chance that he likes YOU and not just the female body.