Really skinny after giving birth need advise?

before i got pregnant i was 118 and my highest weight while i was pregnant was 184 now my son is 9 months old and i weigh somewhere arounf 120 but i thought/hoped i would keep at least some of the weight from my pregnancy but now i just look really skinney but i eat all day every day i've had a high matabolism sine i was born but i just wanna gain some weight i dont look sick or anythin you cant see my rib cage or anything like that i would just lke a little extra meet on my bones/ i've heard of sometimes women get skinnier after giving birth, why is taht and what do you suggest to do to gain some weight and if anybody has anything negative to say or think im crazy F you