How to build self-confidence? Please, tell me some advice, it's not an attention seeking question?

Hey everyone, I'm trying to get some advice people tell me to talk to friends and meet new people stuff like that but I have some issues, so here it goes...
I've ever been a shy guy but I had a good self-esteem a couple years ago because I had a great family all united, great school grades, quite good physical appearence, I hadgood results with my sports team, girls kinda liked me (always as a friend, yeah i got friendzoned a lot) and my friends were amazing always there to help me and we had great laughing times, sleeping over, parties, nights out you know..
But unfortunately my dad had to go to another country by January 2013 because here there was no work left... There was when things started happening.
Later my mom and dad divorced (i guess it was in May) and was pretty hard to deal with.
In october, one month after school started I received the news that my mom got transfered to a place 2000 miles away from here so I would have to move.. and that was devastating.
My school grades began to suck because I was always distracted thinking about other stuff than school, so it was a lot of pressure.
I started cutting in November and it kinda helped me, I guess. When I finally moved in December it was the worst Christmas ever (me, my sister and my mom). I started getting depressed and being a loner. My mom started to noticing the difference and a few weeks ago I got diagnosted with Dysthymia and Social Anxiety.
By the way, I realized that cutting wouldn't help at all and i stopped completely. (I felt really happy when I got one month straight without cutting, it's good, isn't it?)
I hope any of you actually reads this, i know it's big but I need to help to start building some god damn self-confidence because I'm already 15 so I should be looking after girls and not beeing eating and sleeping at home all the time.
Sorry if i looked like a stupid kiddy boy just seeking for attention..
How to build self-confidence? Please, tell me some advice, it's not an attention seeking question?
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