After having sex and using contraception.. I got my period but it lasted for 2.5 days... so just to reassure myself... 2 days after my due date I took a pregnancy test and the result was negative.. after a week I repeated the test.. and the result was still negative , do I need to worry anymore ? I'm too confused.

Hey, I have 2 kids and I found out from the 1st test that I was pregnant. You have started your period and had 2 tests its unlikely you are pregnant. Its normal to sometimes last 5 days or less with your period, I last 2 days sometimes more. Wait for your next period if you don't start then have a pregnancy test.
Good luck, don't worry.