I had unprotected sex the decwmber 27 and the I took a home pregnancy test it was positive I don't know my last period how far along would I be?

About 6 weeks. If you conceived on december 27, that was 4 weeks and 3 days ago, making you 6 weeks, 3 days pregnant with a due date of september 20, 2014 because we date pregnancy from the last period and in a normal cycle the period would be 2 weeks before conception. A trans-vaginal OB ultrasound would give a very accurate due date.