hi, i dont know if anyone else has had similar problem. you'll probably hate me for this and tell me how lucky i am that i'm so slim, but its upsetting me so much 
firstly i want to make it clear that i do not have, nor have i ever had any eating disorder.
i'm not underweight through any fault of my own, i'm just naturally like this, but i don't want to be because i'm desperately ttc and my clothes dont fit properly. both my parents are very slim so part of it's hereditary, i also have a very fast metabolism. i don't really excercise cuz i'm scared of getting any skinnier. i probably eat more than the average woman does on a normal day because if i ate the same amount most women seem to i would pass out from hunger cuz its just not enough for my body. i can eat a huge meal and feel uncomfortably stuffed for 10 mins or so, after about 30 mins i'll feel starving hungry again. before you ask i dont have worms which is what my dad is always saying.
i burn calories off quicker than my body can absorb them. for this reason i have always found it extremely difficult to gain weight. for the past 4yrs i've said every january "this year i want to gain at least half a stone" but it hasnt happened yet (only a few lbs through pregnancy).
i'm a clothes size 6, 5'2" and weigh 6st 13lb. bmi is 17.7 and my periods have always been regular.
i weighed less than this when we were ttc before and i managed to fall pregnant (have kept a few lbs of the baby weight thank god!).
i had morning sickness from about 6wks and had to literally force-feed myself cuz everything made me feel sick. i was still eating, but not as much as i normally would have done.
after my mmc at 8 wks, my mum very comfortingly (not) said "it was probably cuz you're underweight and you werent eating properly"-WRONG THING TO SAY!
but now its got me thinking that it WAS cuz i was underweight and now i'm scared it'll happen again unless i start gaining weight, but like i say i've tried and tried and dont know what else to do!
any advice or thoughts welcome

firstly i want to make it clear that i do not have, nor have i ever had any eating disorder.
i'm not underweight through any fault of my own, i'm just naturally like this, but i don't want to be because i'm desperately ttc and my clothes dont fit properly. both my parents are very slim so part of it's hereditary, i also have a very fast metabolism. i don't really excercise cuz i'm scared of getting any skinnier. i probably eat more than the average woman does on a normal day because if i ate the same amount most women seem to i would pass out from hunger cuz its just not enough for my body. i can eat a huge meal and feel uncomfortably stuffed for 10 mins or so, after about 30 mins i'll feel starving hungry again. before you ask i dont have worms which is what my dad is always saying.
i burn calories off quicker than my body can absorb them. for this reason i have always found it extremely difficult to gain weight. for the past 4yrs i've said every january "this year i want to gain at least half a stone" but it hasnt happened yet (only a few lbs through pregnancy).
i'm a clothes size 6, 5'2" and weigh 6st 13lb. bmi is 17.7 and my periods have always been regular.
i weighed less than this when we were ttc before and i managed to fall pregnant (have kept a few lbs of the baby weight thank god!).
i had morning sickness from about 6wks and had to literally force-feed myself cuz everything made me feel sick. i was still eating, but not as much as i normally would have done.
after my mmc at 8 wks, my mum very comfortingly (not) said "it was probably cuz you're underweight and you werent eating properly"-WRONG THING TO SAY!
but now its got me thinking that it WAS cuz i was underweight and now i'm scared it'll happen again unless i start gaining weight, but like i say i've tried and tried and dont know what else to do!
any advice or thoughts welcome