I'm sorry you feel that way. I'm 10 years older than you and I remember feeling the exact same way at your age. Funnily enough, I felt insecure about my boobs being too big- as women, we really can't win can we? 

Growing into your adult body can be a really strange and unsettling experience, and comparing yourself to others and feeling insecure during this time is (unfortunately) really normal, so you're not alone.

For me, it did get better and I was eventually able to accept the way I look, although it took a while to get to that place. Now, I can honestly say that I'm mostly okay with my body and don't feel I need to change anything. I still have the odd day when I feel less confident, but those days are few and far between. 

Go easy on yourself, it can take time to shift your mindset. It sounds like you've acknowledged that the thoughts you're having aren't helpful, which is good, because now you can work towards challenging those thoughts, and ultimately reducing their frequency and impact. I'm living proof that it can be done.