Acne can be really tough for girls, way more so than guys who are less judged by their looks.
A part of me just wants to say accept yourself more, but really...that doesn't make the acne go away. I know some people who talked with their doctors and got an anti-acne medication/pill that cleared up their face up after everything else failed. It's great to say you accept yourself, but when that acne clears up, oh man is it like a weight off your back.
It's not shallow to want to be liked and popular, that's natural.
You answered you're own question. You're in your head and in your "shell." If you did truly accept and love yourself, including your acne, it wouldn't be a problem. Granted, other people would be more accepting if you had clean skin, but you shouldn't let that stop you. Instead of looking at your negative self perceptions, change it up, start complimenting yourself(this works better for girls than guys), Tell yourself you've got a nice ass, even if you don't think it looks that nice yet. Eventually you'll be wondering why you aren't giving your nice ass the attention it deserves by eating bags of chips and sitting on the couch.
Regular exercise, a proper diet and multivitamins go a long way. Exercise will help you tremendously, simply because it puts you into an amazing state. Vitamins keep the skin happy.
Everybody has a childhood, everybody has SOME friends, everybody has lived SOME kind of life. Therefore, everybody has some experience that they can relate to others. When you're talking with others, relax yourself and start really listening to them instead of trying to keep a dying conversation alive for the sake of your own ego. When you really hear what people say to you, your relevant memories will naturally bubble up, so talk about those. If the weather is sunny and great, say so! If its raining and crappy outside, joke about it. If you work in class rooms or in labs, sit near somebody, smile if you happen to catch their eyes, and say "Hi, hows it going?" Or "that test SUCKED" usually gets a knowing nod at the least.
There really is no magic bullet. As for you current situation, you've already isolated yourself(and you did it on purpose). You are stuck in a camp for 7 weeks. Instead of mulling around in your Shell of negative thoughts all day, just embrace the experience as a whole. Open up and feel the moment. If you aren't that skilled socially, so what? You'll just have to learn over time. A 7 week camp turns out to be a great way open up because you can get to know people over time and ease yourself into different groups. Just because people are making friends now, doesn't exclude you from those groups. Look for ways to have fun with others, and they'll naturally see you in a positive light. Feel the love!
If you haven't guessed yet, I used to be a shy, unhappy teen (with acne) who didn't know how to start a conversation! In fact is was so desperate I went looking online for help
. Jeez another long post, go figure.
PS: For the record, acne scars aren't that unattractive on their own. Speaking as a young sexual guy, there can be hotties with acne scars. The scars diminish after a while, and to tell the truth its just not that big a deal as long as the girl takes care of herself. Hell, I don't even mind a breakout once in a while after I get to know the girl more. My secret friend crush(PU guys, read: oneitis) gets bad forehead zits during exams. Sexually speaking, its only really a turnoff for first impressions, after that its only a minor issue. Zits are tough. Thankfully there are tons of products on the market that deal with this too.