HIV can be acquired by oral sex and the risk might be higher in the presence of blood or breaks in the skin or oral tissues. However, the numerical risk still is tiny for any particular exosure, probably no more than 1 chance in 1000 or so, even if your partner had HIV; and since he almost wasn't infected, your actual risk was too low to measure. Transmission from mouth/throat to penis probably doesn't occur, or so rarely as to be disregarded (no more often than 1 in 10,000 exposures).
In newly infected people, a standard antibody test at 3 weeks has about a 50:50 chance of being positive, so a negative result would be somewhat reassruing. But if you remain nervous, have a 6 week test.
As you apparently know, group sex with multiple gay men is a very high risk activity in general. If you limit your exposures the way you did this time, you're probably OK. But consider joining groups only if every participant is willing to state unequivocally they have been tested and negative for HIV within the preceding couple of weeks; lay off anal sex entirely; and have condoms handy in case judgment (about anal sex) fails in the heat of passion. Or just lay off the group sex entirely.
Good luck-- HHH, MD
Am I correct in stating that?
HHH, MD