I've changed a ton since my Middle School days. A even more from my childhood. Actually one of my main problems (especially noticed by women) is that I rarely stay in the same place very long...I always want something new (which isn't the best way to live)...However, it's been very fulfilling and made me mature beyond my years (or so I'm told).
But, let me preface this with the statement: there is no drawback, aside from health, to being fat. Fat people can bang as many hot chicks, have as many friends and as many experiences as skinny people or 'hawt' people. It is a myth that being attractive is linked to the ability to attract others to you (in any sense).
Life starts with confidence, and you strike me as someone who lacks it. You cannot make yourself the stranger and loner of the crowd and expect to get by. While that rugged "grab life by the balls" style might not be for you, you have to put yourself out there in some fashion. Find something you enjoy (outside of posting on a website) and use it to connect to people. I enjoy working out and make it a focal point and way to meet people and women and gain experiences. While it's not the only thing I use it's highly effective for me.
You need not be afraid of life because life is only truly scary if you never live it. You will face rejection, you will face failure, you will face sadness and you will face hard times...but those who face those the most and survive are the most successful while those who don't at all amount to nothing. Life is only as fulfilling as you choose to make it.
And also, don't be afraid of drinking. I used to be (for health reasons), but I found it was an excellent way to meet people. Being drunk WITH your friends is among the best bonding experiences you can have.
Being yourself does not include being afraid of yourself.