In some cases, even 10 to 14 days following intercourse is still too early for testing. This is because your body may take longer for implantation after conception and ovulation. Since sperm can survive in the human body for up to five days, it is possible for a woman to conceive several days after having sex. Thus, if you received a negative result one week later, you should do the test again. This increases your chance of getting an accurate result.
Source
Menstruation and Conception
Human chorionic gonadotropin (HCG) is the pregnancy hormone. A woman’s cycle starts the first day of the menstrual period. The menstrual period commonly lasts for 3-7 days. As soon as the period ends, the hormones begin working to prepare the egg for ovulation. Generally, ovulation is on day 14 of the cycle. During this time, the ovaries release ovum. If the ovum is unfertilized, it remains for about 5-8 days in the female genital tract.
False Negative Test
If a pregnancy test is performed on the first day of your missed menses, it may provide a false negative result. The common cause of this is early testing. Sometimes, even individuals with very high levels of pregnancy hormone can receive a false negative result. If the test result comes back as a false negative, another test can be taken again the following week.
Pregnancy Test Availability
Any local pharmacy, grocery store, or drug store will have testing kits available for purchase. These are less expensive. At certain health care centers, they are available free of charge. You can also get one from your nurse or doctor.
