Is the 70th day negative result reliable for the 3rd generation hiv test that only looks at the antibody? if not, should i retest after 90 days or when should i retest?

Unless you have developed acute retroviral syndrome (fever, swollen glands, sore throat, rash, muscle/joint pain, diarrhea, and headache), I would recommend 4th generation combination antigen/antibody immunoassay plus HIV viral load test at 90th day. 4th generation combination assay plus viral load test seems to detect nearly 99% of early HIV infection.

Get a 4th gen test at 90 days, however, HIV is only one of the STDs. A condom may not protect against HPV, Herpes, LGV, syphilis, pubic lice etc. It would be prudent to see your doctor for an evaluation. Visit this site for information: https://www.cdc.gov/std/default.htm Wish you good health!