I've been getting a lot more involved in school activities this year - just got back from a long day of setting up homecoming decorations, in fact. It's more work than I expected, to be honest, but it's also really nice to be working with other people and helping out and stuff! And my heavy involvement with the school's Speech Team might do a lot to patch my slight inability to talk to people. -w-

In any case, you shouldn't take what I say as a reflection of who I am, I am very much still trying to determine that...
I know exactly how you feel. My school's workload is so heavy that everyone in my grade constantly jokes about, "Life? What life? There is only homework." In reality, half of us cry ourselves to sleep at night.
My suggestion is to drop a few extra curricular if you must. Also, realize that not all grades are important. I maintain a steady 90-98 set of grades in all my classes because if an assignment isn't worth a lot, I half ass until it's done.
I also budget my time using Google Calendars. Every day is planned down to the minute, with about four hours left for free time. I guarantee that if you plan things effectively, you will be less stressed. Also, I suggest that you limit homework time to a maximum of three hours with the occasional exception for major projects. School is not worth your sanity.
Also, tell your parents that you are stressed. Tell them that you can't function without communicating with your friends for emotional support, and your phone is your link to that. If they don't understand, if they tell you "no", then treat them exactly the same way. When you have nothing left to lose, you can afford to take risks.