If the ovulation test paper appears strong positive, it will usually last about two days. If this happens, it means that the luteinizing hormone in the urine has reached its peak, which means that the ovaries will ovulate about 24-48 hours after the peak occurs, and it is recommended that you can choose the time of coitus, which will improve your chances of getting pregnant. And it is recommended that after intercourse, you can collect morning urine for about 20 days and do an early morning pregnancy test to find out if you are pregnant. If you want to take a blood test, it is best to take a blood test 15 days after intercourse to check the blood HCG to know whether you are pregnant or not.