From what I understand, the interactions you talk about happened away from the workplace, in an apartment. As such, it is unlikely that HR could get involved. Still, document anything that happens, whether in the workplace or not. If something does happen that is within the purview of HR, all of it will be relevant.
I am sorry to hear that you have to put up with this crap. I thought you liked this workplace, so it must be disillusioning to have this going on.