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Even a drop of semen is enough to get pregnant. If you are not planning pregnancy
i advice you it is better to go for one or the other method of contraception
As you have done the pregnancy test very early there are chances of it being false negative.
It should be done a week after missed period, preferably using early morning urine sample.
I advice you to repeat the test after a week of missed period. As you are delayed by 3 days i advice you to wait for another 4 more days and repeat the test.
Depending on the result you can consider your next approach.
Hope i have provided the information you needed.