17 and no social networks?

[...yo]

I'm a 17 year old guy and I don't use any social networks. No facebook, instagram, twitter, vine, etc. The only thing I ever had, when I was 11, was Aim lol. After that I just never cared. Then, I realized that things like facebook and instagram strengthen friendships and relationships. Everyone around my age has an instagram and has seen "that" vine video except me. And I know the reasons; I believe my old friends from middle school (who were, at the time, my best friends and also girls who had crushes on me) don't remember me anymore since it's been three years. And also, I used to have severe eczema as a child (but it cleared up and I look like a normal person and have looked like one since I was 12) and it really hurt/hurts my confidence. Like I have no confidence in my self/ my appearance. What should I do? I really want to use them now so I can reconnect with my old friends and people I still care about but theres always that one factor in my past that holds me back.. help?