I am underweight. Ur valuable response.

Hi..I am 32 yrs old lady,I have a problem with my body weight,I have a very good diet from childhood,I eat almost 700 calorie food a day to increase my weight but my vody weight is still less,I m going to depression day by day due to image issue,others eat very less still they gain weight but me instead of having a diet like a mature man my body is still like a 6th standard girl.I m married but due to this image issue m not stable in my life.I need serious attention ,My weight is 52 kg and height is 5"7.Kindly help me .i want to put on as much weight as possble.As i have been trying to put on weight from my college days but still a failure.Need your help doc.Kindly suggest me some strong steroid which will increase my weight to max. Waiting for ur valuable response.