"i lost my virgin(unprotected sex) on 27 dec 2012, last menstrual period was on 2 December ,my cycle length is 28 days,up to now I don't see my menstrual period and I was supposed to start my period on 30 dec 2012,does this means that I'm pregnant?

You could be. You'll need to wait two weeks after your missed period, then take a test with your first morning urine. Two or three days is not considered late.

How is this possible to have pregnant when someone have sex 3 days to the expected date of menstrual flow.I saw thin mucus(I told this is sign of ovulation) which ended on 19 dec 2012.

Who told you to have unprotected sex and after ask these stupid questions here!!
Consult a doctor or use contraceptive pills!!