Scared to gain

Hi! So I am new to this whole forum thing and added because of all the inspirational posts people put on here about gaining weight. I am 5 ft 4 and weigh 105 lbs. I am 19 yrs old and sadly have lost my period. People always mistake me for being alot younger than I am. I want to gain weight not only to have more energy so that I can continue to enjoy my workouts (I love exercising) but also because I want people to look at me and know I am a woman not a child. I haven't talked w/ anyone about this; they assume I have just always been skinny. I was wondering how many people out there like the way they look after weight gain because I am really scared I will hate the way I look after I gain. Also I don't really know what my goal weight should be.  Thanks.

A healthy weight for you would be between 112 and 143lbs.  So given that you only need to gain 7lbs to hit the first marker chances are that you wouldn't look noticeably different to the way you do now.  Aim for a mid-point in that range.... 120lbs or so... and you'd probably start to look more womanly i.e. slim but with more pronounced hips, breasts and a defined waist.  Which sounds like what you really want.... you seem to hate the 'little girl' way you look now.  

As you've lost your period you really do need to go to see your doctor.  Long-term amenorrhoea can be indicative of a gynaecological disorder as well as being caused by over-exercising or a poor/insufficient diet.  It can lead to many other medical problems if left undiagnosed and untreated.  Professional advice on diet and exercise and supervision from your doctor will almost certainly be more effective than trying simply to go it alone with a difficult problem.