Is my figure messed up? or is it just me?

ok so..im a 17 year old guy... about 2 years ago i used to weigh 100 kgs. I started a diet gym etc for 2 years and i managed to loose 35 kgs , yep thts right i weigh around 65-70 kgs now :) . A rly big achievement. One problem, i seem to have my hips jutting out its kind of strange. Its not really noticeable with a shirt on but it kind of messes my figure up a little bit. i dont think its fat its just bone. My ribs are showing and everything. Ppl tell me i should go to the gym and get built but i dnt know what i should do :S... pls help??