I took a 5th gen ag/ab test 39 days post exposure. non-reactive. am i ok? should i retest at 12 weeks?

Retest: Retest as you have mentioned. To be sure, get a HIV nucleic acid test at 6 months after potential exposure. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.

Nearly conclusive: "5th generation" is marketing hype by the test manufacturer. It's essentially a 4th generation HIV Ag/Ab test. Those tests are nearly conclusive after 4 weeks and 100% by 6 weeks. 39 days is very close, but to be absolutely certain, have another test at 6+ weeks. There is no need to wait until 12 weeks. Later testing (3 or 6 mo) is not necessary; old news from older HIV tests now not used.