update height and weighht (also need weight gain help)

[skt2310]

Im 15 turning 16 very soon I was 5'8 i think at the beginning of this year now I'm 5'11 still growing, I weigh at a raw 138 pounds when I eat by the end of the day Im around 148-149 but overnight somehow I lost all of the pounds and im back at 137-138 how is this possible? How do I get past this and gain weight by the way I am 138 lean muscle