Dear Daniel C:
Homework for you is very unpleasant so naturally, you are not motivated to do something unpleasant and so often…and 3-6 hours per homework assignment. Communicating online is pleasant, so … naturally you prefer that. And your parents getting annoyed with you is unpleasant..
Just like any living thing, any organism, we move toward what is pleasurable and away from what is unpleasant, distressing and painful. This is not only human nature, but animal nature.
I hope you can communicate to your parents that their annoyance is unhelpful to you and acts against their own interest to motivate you to do homework. It may work for a short while but on the long run, day in and day out, it works against your efficiency as a student.
Then if you are diagnosed with GAD, perhaps you can use that diagnosis to convince the principal to direct teachers to lighten your homework load.
Next, be okay with taking a break when doing homework, ten minutes or so every thirty minutes or an hour and go online. Then back to homework. Breathe deeply every once in a while. Have your parents bring you hot tea in the winter or a cold drink in the summer as you work. Make it less painful and more pleasurable (work with the withdrawing from pain/ reaching out to pleasure principle of nature).
anita