HELP PLEASE!! an Ongoing Student Overstayed in Australia, What Should I do?

[asterian]

Hi guys, need a help here. I realize that I'm in big trouble just this afternoon and currently I'm very-very panic.

This is the story:
I am an international student, sponsored by AusAid, suppose to finish my study on July 2008, but due to healthy problem I have to suspend the study for a semester (January to July) went to my home country and went back to Australia by mid-July and will continue to study until February 2009.

Currently I have an Australian visa until 31 August 2008 (originally designed for 18 months study) and has overstayed for 20 days without realizing how deep my mistake is until this afternoon. Where I told my sponsor for a couple of time the wrong date by mistakes and had no intention to deceive them at all.

I need a legal advise and these are the questions:
1. What should I do??, I already contacted my sponsor and my consulate general, but no responses yet, maybe because this is weekend and they're not around until Monday.
2. Should I contact the nearest immigration office and probably doing "kamikaze"??, please consider that I should have another 6 months to finish my study.
3. Will the ban to enter Australia for 3 years will be applied to me??,
4. What are other possible consequences of my mistakes??, other than detention, deportation and fine.

Thanks for the advise guys, really means a lot to me.