What am i doing wrong? how do you gain more confidence?

i don't mean to sound vain or anything, but i've known for quite a while now that i am very attractive (i don't exactly know how but quite a few people have said i am). it seems like half the girls i meet always end up flirting with me. the only problem is the fact that i have confidence issues around girls when it comes to the more "seductive" situations (i have no problem around them as friends). i always end up becoming very frigid. now i've developed some stupid reputation of being a heart breaker and confusing them, even though i don't intend to. It's just that when it comes to the more intense moments, i always end up becoming very frigid. how can i change this? are there any good ways which could help to gain more confidence around girls? most my mates find it crazy how i don't do anything with most of them.