Feeling beautiful is in your own mind. Just like if someone feels they are important or interesting. Its all in the mind. If you are low then you will never feel very positive about yourself, thats how it is. If you are overconfident, you will feel you are 11/10 at any of the above. You know how your feelings can alter your moods and thoughts, decisions and perception.
In other cultures women are all perceived as beautiful because they are supposedly the gentle gender and the child bearers, the nurturers, the peace makers. In my culture as long as I look and act like Rhianna or Shakira or Miley, then sure Im beautiful definitely

Its all about perspective, your own based on what you are told externally.
You are young right? Please stay away from mainstream rubbish in the western world (Im a UK english woman) it will eat away at you 24/7. Such a shame we are bombarded with vanity all the time, makes us spend too much time worrying about if we are `right' and `perfect'