We do not consider receiving oral sex as a risk for HIV. Therefore, you should not have to repeat the HIV test for the oral sex you got 4 weeks ago.
However, it is possible to get other STIs when you receive oral sex. These include Chlamydia, gonorrhea, HPV, herpes and syphilis.
Your urine tests done at 4 weeks should have been accurate for gonorrhea, because most results are accurate after 7 days. The test for Chlamydia is most likely accurate at 4 weeks, but it can take up to 6 weeks to show up.
The blood test for syphilis, done at 4 weeks, may be a bit early. Most tests will become positive within 6 weeks, but it can take as long as 3 months to show up.
As for HPV and herpes, we usually diagnose them when we see signs of them. Check out our pages on herpes and HPV.
You might find it helpful to look at our “STI at a Glance” chart. It gives information on window periods and you can see when tests will be most accurate.
You may want to repeat some tests, such as Chlamydia and syphilis, 6 weeks to 3 months after the contact you had.
Please leave a comment to let us know if that answers your question or if you need more information.