I still contend this guy is a player and will take it wherever he gets it. But it is pretty clear you were determined to make something like this happen, so we can't blame him too much for going along with it.
The problem isn't with you "cheating" in an M that has long been over, it is with how you are treating yourself.
This smacks of: treating-myself-so-badly-and-f***ing-a-stranger-will-be-just-the-trick-to-shake-H-up-and-make-him-come-home sex. There is no way such sex would be good.
As for not practicing safe sex, there is no acceptable excuse. If nothing else, think about your kids needing a healthy mother.
You will not know your HIV status for at least six months, so you might want to see if the guy will take an OTC HIV test that you pay for and mail to get his results yourself. In future, keep in mind that condoms do not offer protection against, for instance, Genital Herpes, which is carried by something like 20% of the population.
Take better care of yourself, you deserve it. And stop talking to STBX about your sex life, that is really very unhealthy enmeshment. Let go so you can have a good life.
