I made love to my girlfriend while she was crying and now shes pissed.?

My girlfriend is really into " play" and has asked me to tie her up and such things in the past. Recently after a particularly emotional night we had some of what I would have considered make up . It was rough as usual and i heard her sobbing. Since I was taking her from behind I couldn't see her face and I simply asked if she was crying. We have a safety word so I had no indication that she wanted to stop and she claimed to not be crying so really I just thought it was happy moans. Well after I finish she gets up and drives home in a huff. I call her multiple times and she finally picked up and told me that I was a pig for not stopping. We have a stop word and she didn't use it AND she told me she wasn't crying. She said "I'm just a typical ******** guy". This isn't fair! What can I do to explain this to her she keeps telling people I forced it on her and stuff.