The question I would ask is what, if anything changed in your life a couple of years ago, when the anxiety symptoms began to appear? You clearly have a sense of some of the contributing factors (though I don't think that masturbation is one of them, and it might help you relax, if anything) so I would start with becoming more vigilant with your diet, eating healthy meals on a regular basis, (3 square meals, two snacks to keep blood sugar levels even) and getting a good balance of nutrients. B-complex vitamins and Omega Fish Oil (high EPA especially) can be very helpful with both anxiety and depression. You might want to try a supplement by NOW nutraceuticals called "True Calm," which can be very helpful. Passionflower, valerian, lemon balm and other herbals can be helpful too.
You should shut down your computer at least an hour before going to bed, and try to do something more relaxing. Take a shower or bath, do some light reading, with lights down low. Try some deep breathing or stretching exercises, or yoga before bed. Lavender essential oil is also very relaxing - you could apply a couple of drops on your temples before getting read for bed. It is a proven anti-anxiety herb.
You need to get regular exercise to work off steam. Try to get out for 30 minutes a day if you can. And if you are really "hopped up" I'd do something vigorous like running, biking. Vigorous exercise releases endorphins and serotonin, which lower anxiety.
I think the you need regular interaction with people in your life to feel more calm. This is huge! All the better if you can have *meaningful* interaction with others -- good conversations and good times. They say that "people are Prozac," and that we need several hours of interaction with people each day, to feel good about ourselves, and all the more so if you are an extravert. It you find that you are isolating yourself because of your anxiety, it might help to force yourself to go out for a walk, to a coffee shop, to get some exposure to people, even if you aren't connecting with them personally. If you are living far away from old friends, can you connect with them by phone, or Skype? Facebook and online activities are okay, but they don't replace face-to-face interaction. Are there ways to get around the cultural barriers to your current isolation?
You might also want to check out books by Dr. David Burns, such as "Feeling Good," or "When Panic Attacks." He is the leading expert on cognitive-behavioural techniques to help people heal from anxiety and depression.
Hope this helps! Lots of people suffer from anxiety, you can do things to feel better.
Not interested in anxiety medication. Otherwise, I've tried most of that not including therapy.
Even those that lead the healthiest of lifestyles can still suffer from anxiety.
Are there other factors that might be contributing to it, such as work related stress, family, social anxiety, something along those lines?
Have you tried therapy? Spoken to a doctor about possible medical causes? Have you ever been on anti-anxiety medication? In the meantime, exercise, relazation/meditation/yoga have given many people great relief in their anxiety issues.