Everybody have different preferences. It is true that the majority of men will prefer feminine women, but some will also prefer girls with a more hippie/rock vibe or tomboys. Opposites attract, so in the same way girls have different preferences. You can see it this way; a certain % of men will prefer "boyish" girls and the same % of women will prefer less masculine men. I don't have a problem with "thin" guys, although I will admit I don't like the clothing style you describe.
If you feel you're lacking in confidence or that your appearance don't match your personality, you can work on that. But to answer your question on what attracts girls - a number of things, but masculine is an attitude and a behavioral pattern, not an appearance.
In my experience, through my entire upbringing, the 'popular' guys have been those who are confident, charismatic, funny, cool, good sense of style, usually well off (being from a wealthy background does in fact give some guys a confidence other guys don't have. They are often more likely to be well-traveled as well). Although not all of those things are achievable, my point is that it has never been the most bulked-up guys who get the best girls. I've observed it in some working class environments, where "health studio" guys like you see on TOWIE are popular, but for most people, the way a guy carries himself is the most important.
But in general, the amount of women who prefer feminine qualities in men is obviously smaller.