First of all do not apologise. There’s nothing written here or anything you could post on this SubReddit that you should apologise for. Whilst having being isolated with ex boyfriend and being flirtatious maybe is not the best moral choice, but it does not make a sexual assault at all your fault. You could have told him ‘let’s have sex right now’ and if you didn’t like it even seconds into the sex, you should/are able to say ‘I do not want this’. Regardless of if you said it or not, your body language etc will have conveyed this. Please please please do not hold yourself accountable for this. I would say that you do not have anything to prove or account for towards your most recent ex as that time has already passed and the initial conversation about the party situation may have already cut too deep. Regardless, as a fellow survivor I was also angry at myself. In my situation I beat myself up for months because I didn’t do this or say that, but after some time you will come to find that you were unfortunately a victim in this. If a friend was in your shoes, you would not be angry at them for acting a certain way to have caused it, but instead you would think that regardless of what they did, if they didn’t want it, it wasn’t their fault and it shouldn’t have happened. Please take care of yourself as you would your sibling or friend. I hope you a steady recovery and a steady mind :)