Of course condoms should be routine for casual or non-monogamous sexual encounters involving vaginal or anal intercourse, but a brief unprotected exposure like yours is unlikely to result in any
infection, even if your partner had an active STD.
While I would not have recommended azithromycin without prior testing, it probably did no harm and provided good protection against gonorrhea, chlamydia, NGU, and syphilis. Azithromycin commonly causes the gastrointestinal symptoms you experienced.