Those years around the end of high school and the beginning of college can be tough. I had a tough time as well around that time. Hang in there and remember that life can improve even if things are very difficult now.
I'm not qualified to be anyone's Buddhist teacher, but I'll give you a few of my thoughts (I practice Tibetan Buddhism, so my thoughts are from that perspective).
I think you're probably experiencing these difficulties as a result of negative karma created in past lives, so the way to counteract this is to create good karma. But take heart: the very fact that you are now interested in Buddhism is itself very good.
If you want to stop your constant internal dialogue and create good karma at the same time, you could try reciting the classic and powerful mantra OM MANI PADME HUM. Here's some info about it:http://www.dharma-haven.org/tibetan/mea ... e-hung.htm
Or if you feel you want to relate to a caring, enlightened, female bodhisattva try Tara's mantra OM TARE TUTTARE TURE SOHA.http://www.wildmind.org/mantras/figures/greentara
According to my lama, saying these mantras out loud purifies energies in both your mind and body.
I too know what you mean about wanting to help people, but being awkard when you do it. I'm still not very good at helping people, but I'm improving. Part of the reason I like teaching is that I feel I can help people as part of my daily work. My students have forced me to get rid of a lot of my awkwardness and have allowed me access a kinder side of myself.
But I think the important thing is to do something nice for others, even if it's very small. Give a homeless man a dollar, turn a beetle rightside up which is stuck on its back, take out the garbage for an elderly neighbor, help someone with some chores, drop some change in a donation box in a local church, etc. There's always something to do if you look. Spiritual practice isn't always exotic; sometimes simple everyday actions are the best way forward.
And when you feel it's the right time and you feel good about it, you could take refuge with any Buddhist priest in your area. Taking refuge with a Buddhist priest of a certain sect doesn't limit you to only following that sect, and taking refuge is an extremely positive action which you will benefit from in this life and in all your future ones.
I hope you will be able to create many blessings for yourself and others and overcome your difficulties.