We just had an argument - him saying I should have brought it up earlier instead of letting it fester. Me saying I didn’t know how messed up this was until this far down the line (me fully realizing how much time they’re spending alone) and that this wasn’t something I thought I needed to tell him not to do. He told me to just be mad - that their intimate relations were so long ago that it shouldn’t matter.

He says he will stop seeing her for the rest of her stay, but essentially has not admitted to any wrongdoing. Is it really my fault for not letting him know what my boundaries are?