I lost my friends cause i dont use social media?

[...yo]

I'm a guy, 15 years old, and i've been feeling kinda lonely ish lately. Let me go back a bit:
When i was 5 to 9 years old, i had skin problems (eczema). It was horrible too. My legs were cut up badly, feet, hands, and arms also had cuts. People would ask why my hands look weird and i became very self conscious. In the 1st grade, my teacher didn't understand my issue. If i even itched my arm once she'd send me home. My parents were getting frustrated, having to pick my up early almost every day. In 3rd grade, i made a bunch of friends in the same class. For the next two years us 30 kids, and i had a bunch of other friends in other classes too, had been in the same class. We were all really close. When i graduated, i had hoped to move on to the same middle school with my friends, but my parents transferred me to a middle school a bit far from my elementary school area. But it was still in the same city. My social life was sort of reset after that. Friends back to none. In the 6th grade i met like 40 kids by the end of the year whom i was close with. In the 7th grade i knew many more. And by the 8th grade i knew every single person in my grade, didn't know them all well but i knew them. Those 3 years were the greatest of my life. My skin problems went away 99% in the 5th grade and fortunately never came back. Yet again it was graduation time, and i went to a good high school, but my many friends didn't end up in the same one as me. I met about 50 different people in this high school, i know many more though (just their names and maybe talked to them once or twice).
Recently, i've been missing my friends badly. I feel lonely, possibly even depressed. During my recent winter break, I was playing a game called call of duty, online on my playstation 3, and my old middle school best friends were online too. We reconnected that whole break and laughed and talked and we missed each other.
My parents were/ are very strict and they are very serious about my school grades. They yell at me so much, and i just really hate them. My brother is an a**hole (he's like 11 years older than me). He tells me how i have no friends and thats why i don't use instagram or facebook etc. He thinks he's so cool when he's done with school and only has 380 friends on his facebook.
The truth is, i've been through so much emotional pain in my life, especially as a child, that after losing my friends (not literally, just going to a different school each time after graduating from one) twice already i just don't have the confidence to use facebook or instagram. I hesitate when talking to girls now when i used to be so smooth and nice. I was always nice to my friends, still am, because nobody ever was to me before i met these people from my middle school. I don't give a damn about my family.
How can i get myself to use facebook? Then progress to instagram and other things and just be happy and normal? I feel so shy that i'll end up with like 100 or 200 friends while all my other friends have like 800 to 2,000 friends. Or that my old middle an elementary school friends will not remember me :\. Sometimes i just feel like going on, and just constantly adding people for a good hour, but then i just feel like i have no confidence to do it and decide not to... Help me please? I don't want to feel like a loser :'( The only time i was ever happy was whenever i was with my friends. Although i still made new friends here in high school, i want to keep them close to me but also reconnect with my old ones but i'm worried i'll end up with a few number of friends added on facebook, i know it sounds dumb, but i can't help it..