please respond: seriously scared for my life

hey ladies! i had unprotected sex on December 3rd (2days after my period ended). he pulled out and was only in for a VERY short amount of time because we had been "fooling" around before. i took plan B just to be safe. i bled about 3- 4 days later. my period is now 5 days late. it's been exactly 4 weeks since this happened and ive had 4 NEGATIVE TEST!!! can someone please put my mind at ease?!? i cannot be pregnant!!