I want to ask about two things that are bothering me alot. ?

headaches are very normal during pregnancy. they are caused by an increase in hormones. as far as your weight is concerned, I wouldn't say that you are under weight but it depends on how much you weighed before you got pregnant and so on. the average weight for someone your height according to my doctor (and so you know I think that these numbers are completely insane) is between 125 and 130 lbs. and you weigh around 138lbs so if you were what my doctor calls average to begin with then no I think it is perfectly normal weight gain.