Hello, Welcome to HealthcareMagic..
As per you told your periods not came as per your normal shedule. You had sex 4 weeks ago and you are fearing of pregnancy
and for the same you had made confirmation by urine pregnancy kit but unsatisfactry result..
Please be clear in your mind htat sex in safe periods of cycle not leads to pregnancy. And to confirm pregnancy the pregnancy kit are not 100% reliable.But it is important to rule out pregnancy. This should usually be done 2weeks after missed period for good result and using early morning urine sample For 100% confirmation of pregnancy USG scan is very specific.
Have a healthful Day..