When I was your age (I'm 16) I was about 125 and 5'5".
Although it really depends on different factors, such as how much muscle you have.
My username is an incredibly stupid pun that only I will get.
Currently working on:
Scarlett O'Hara Drapery Dress -- Gone With the Wind
Deandra -- MPGiS
Anna Cornonation Dress -- Frozen
Vader Eloha/The Queen -- OFF
Princess Suwa -- Mascot of the city of Suwa, Japan
My favorite cosplays:
Brittnay Matthews -- MPGiS
Mom Lalonde -- Homestuck
Princess Kenny -- South Park