HI, Welcome to HCM, I am Dr. Das
First of all, for your kind information, symptoms may also appear even after 6 months.
So, it was better to have a post exposure prophylaxis as soon as you discover the problems.
Whatever, now, it cant be said what is the probability of getting infected. Because it depends on entirely on the persons you had sexual activity. If the have any infection, there is defionitechance of getting infected.
You can do p24 assay after 14 days of exposure if it is negative, then ithere is minimal chance of getting infected. And apart from that you have to do Elisa
test for HIV1&2 after 3 and 6 months.