The point here is that no man or woman should try and change their appearance to please others, period. The only ones they should change for is themselves, without outside interference. If a woman tells you all the little things that are wrong with you - ask her is there is anything at all that she likes! - If another person cannot accept you the way you are then they are not worth your time or energy.
And if they do not like you for who, instead of what, you are, then they are just using you or playing a mean joke. If you let them play with you just to be accepted, make sure your life-insurance premiums are paid and that someone worthwhile will benefit from the foolish actions you are inflicting on your body. Face it, you still will grow, take your time - being a grown-up with all the responsibilities that go with it is not at all a piece of cake - not in this world today. You can in the meantime concentrate on your education, go to the gym and do some normal weight lifting to build up muscles normally, and enjoy being a youth because once an adult, if you get there, you will probably wish you could find the fountain of youth. Get real and start enjoying what comes natural to a young man your age, please.
Hope you are not doing anything foolish just to please a vain little girl who needs a trophy by her side - she's not worth it.