Your problem seems to be linked to self perception and self esteem and you don't seem to have any hormonal imbalance. I would suggest that you should confide in someone you can trust, even if they do disregard it as inconsequential you might get some insight into others perception of your body type. Also I would like to clarify some other facts, such as there are two generic categories of body type such as the pear shaped and the apple shaped. The pear shaped has a tendency to gain weigh on the hips and thighs while the apple shaped tend to gain on the stomach and upper body. There is no strict male or female body type, as a lot of women also have a tendency to gain weight on their upper body and vice versa which shows that your body structure is not abnormal or any less attractive. However, your narrow frame may also be more visible because of your weight (being on the lesser side tends to accentuate your frame), style of dressing etc. So if you have time you could try some controlled weight gain and training at a local gym. The problem seems to have an adverse psychological effect on your daily functioning hence visiting any good counsellor in your locality may also be a good idea.