Did you have unprotected sex? Test with a duo test at 4 weeks
No protection sexual intercourse is risky, unfortunately duration is not that much important, so you need a test here.
Then to second question 3th generation test are very good but they only search for Antibodies, So a 27 days test is not giving us actually any useful information, a 6 week 3th generation would be a very good indication, as doctors usually accept that as a very good golden time to test.
So in your case I offer you do a 4th generation test after 8 weeks (if you have stress) or wait till 12 weeks and do another 3th generation test. All the best,