I agree with everything that's been said so far.
I found a lot of the stress in my life came from general close-mindedness and a lack of understanding about myself. Before, when I learned something new, I used to enter a sort of "I already knew that, don't you know I already knew that?!" attitude, keeping me from learning as much. Simply acknowledging that you're learning something new in school will help you out a lot, along with a healthy curiosity about the subjects the teachers are presenting. If you want to learn more about your personality, take a
personality test or something. Learn from it, recognize it's only an estimation and mostly theory and psychology nonsense, and use it to figure more out about yourself. The one I linked gives lots of details on different types of personalities, just follow the links it gives you.
As for social life... Me? I found that I didn't really need to much human interaction to feel socially fulfilled. If you still hang out with people during lunch, or hang out at all, you're probably closer to others than I am. I have a grand total of 1 person I've hung out with once in the past year. Simply observing how people act and being nice to others when they approach me is enough for me, most of the time. You may have different needs, though, so pay careful attention to your feelings and how you came to have those feelings. Are those feelings coming from external or internal sources? Do you feel like you need more of a social life because those around you do?
If you find that you do have a sincere desire to socialize, the internet is not the place to focus your energies. I'm not against talking to people on the 'net. It's just really hard to get the same emotional fulfillment chatting with someone on-line, or even on the telephone. Most of our social stimuli comes from interacting with people face-to-face, so make it a point to use the internet primarily as a place for advice and general knowledge, and less of a place to fulfill sincere desires for human contact. So, chat it up on the 'net if you want, but don't use it as your go-to source of social interaction.
Something else to keep in mind is that you're in a pretty crazy time of your life. Find a way to deal with the changes your body's presenting you. I recommend two things that will help you a lot: Find a non-violent, low-impact way to exercise (Jogging, lifting weights, tennis, etc) and a hobby (Such as writing stories, growing plants, or drawing pictures).
The exercise will flood your system with endorphins, which are chemicals your body releases naturally and make you feel better, happy, and content. The biggest challenge is finding something you can stick to and getting over feeling ridiculous doing it - I recommend asking a parent or mentor for advice and one-on-one training to start off with. Bonus points if you can find someone who trust to stay friendly playing a competitive sport with, but keep it something you're mostly willing to do, or at least don't mind doing. This will help you in nearly every point in your life, even academics and social interaction.
The hobby will give you some sense of progression as your skills improve, fulfilling your innate desire for progress and improvement and causing your brain to release even more endorphins into your system. Generally, the more physical the hobby the better, since your brain responds better to things that aren't on a computer screen. Draw and write on paper when you can. Save the computer for fine-tuning art and when you actually start writing fleshed out stories. Generally, you want to work with your hands more than anything.
These are things that can help you, or anyone, at any point in life. Remember that you are in charge of your attitude - Nothing and no one determines your happiness or success - Only you do that.