i used to have regular period  lasted for 5 days and my cycle was 28 days until a few months ago. my cycle became irregular up to 39 days but my period remained 5 days. i had my last period on the 12th of october up until now i havent had any. i had sex on day 6 and 7 then from day 20 until now. had a pregnancy test 3 days ago but it was negative. could i be pregnant i am soo worried