Will 4 th generation test after 28 days will be conclusive
I believe the statistic from a single exposure is less than 2% transmission rate. Very uncommon. The two minutes of exposure to unprotected vaginal would be unlikely to transmit HIV. However, you'll need to get tested for that. but as Mike_no said, oral sex is not a risk at all for HIV.
Unprotected vaginal intercourse would warrant HIV testing. Risk is low. You could take a test at 28 days with a IV generation HIV test.
HIV transmission can't be guessed with help of judging any strata of society, geographical factors, sexual orientation or from one's behaviour.
Only testing is the answer. Although, it is seen that CSWs do take utmost care of their own health to stay away from STIs, periodic testing and safe sex are integral part of their lifestyle.