Will a first response pregnancy test give an accurate result about 5-6 weeks after sex? even if i took it in the evening.

Yes.: Your Beta-HCG is highest in the morning. If it is negative, you may want to repeat it in the morning or have a blood test done at your doctor's office.

Pregnancy test: Accuracy of pregnancy test is related to the day of ovulation. The average menstrual cycle is 28 days. Testing after 5 to 6 weeks will give an accurate result. Accuracy is better in the morning when the urine is most concentrated.