how weird i have basically the same stats as you! i am 5'9 and 18 too and used to be about 180 then lost to 150, then recently got too relaxed like you and got back up to 180. I also want to lose down to about 130 or so ultimately. only difference is i dont have a twin! anyway if you want to email me and we can share tips/ideas etc my email is fruit_salad_yummy_yummy@hotmail.com