If you really want to change yourself so you will feel better about your appearance... all you need to do is eat healthy (give up the fatty/sugary/salty/junk/fast foods and eat a well-balanced diet) , try to start doing exercises and your body will change although this'll take time. Weight isn't important , your health is. Last time I tried to gain weight just to look more fat (bcuz I was so thin) by eating donuts and unhealthy stuffs but I didn't feel it but during the time I increased intake of healthy carb-rich (don't go overboard) foods , I gained 5 kilos in 2 months. Pretty great but I know you could do it. I was also a soft-speaker back then but as time progresses I was changing and eventually became better at speeches but I feel I need to improve but my performance was alright. It would just take time!