But that was abuse, and abuse can cause PTSD. Putting you at a risk like that, making you have sex more than you wanted to, giving you a disease, on top of other things.
Is the person who made this thread talking about something that severe, or just cheating in a relationship? I don't doubt that something severe like that can cause PTSD, but I am saying that something like coming home one day and your partner telling you they've been seeing someone else and then getting divorced as traumatic as it may be isn't something that would be classed as PTSD from what I know.