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is unpredictable. Usually we advise intercourse 2 before and 2 days after 14th day (12, 13, 14, 15, and 16). During this period, the chances of fertilization of egg are more. This is because around 14th day of cycle, egg is released.
If your pregnancy test is negative, repeat the test after 3 days. If it is still negative, you have are not pregnant. Urine pregnancy test very reliable test for pregnancy.
Regards, Dr. Jagdish