I had sex without protection one month ago, i have just made a hiv screening test the result was negative, do i need more tests or investigations?

Yes: Recommended screening includes one more test at 3 months.

I would consider: Several factors. One month may not be enough time to seroconvert. It says under conditions hiv, do you already carry the virus? If that was a mistake, does the person with whom involved have a history? If male to male higher risk than male female intercourse, for male. One time experience carries low probability of getting virus. Consider retest in 1 month. Will get more precise answer.Gdluc.