HI, thanks for using healthcare magic
It is understandable to be concerned regarding the possibility of contracting
HIV.
If neither of you have been sexually active before, no history of
intravenous drug use or no history of HIV contracted intrauterine (inside mother's womb) then it is unlikely that there is significant risk of exposure to HIV.
There are different ways of screening for HIV. If you do the PCR test, it can show a definitive result within 21 days of exposure.
This particular test looks for the virus itself whereas other screening test look for
antibodies which are the body's reaction to the virus.
The test which look for antibodies may not give a definitive result for 3 to 6 months.
Since you were sexually active a month ago, you can do the PCR test now to find out if you are positive or negative.
There are other sexually transmitted infections as well.
It would be best to use a condom when you are sexually active to reduce the chance of infection or your partner becoming pregnant.
I hope this helps