Hi! I had a similar situation too. Finally managed to escape my abusive situation, but my abuser still went to the same university I did and so unfortunately I saw him and reminders of him EVERYWHERE. Even after he graduated I felt afraid, couldn't concentrate, constantly speed walked and was short of breath.
Sorry I don't know much of your history, but were you abused on campus? I was and it made it a heck of a lot worse... in hindsight I should have looked into transferring somewhere else. So if that's an option maybe look into it, for your mental health/personal safety. But if you can't/don't want to do that, could you alert campus security to what your abuser did? That might make you feel a little safer, if someone with power to help you knows about the situation.
I think it's like dealing with any trigger, albeit a very intense one... have you got grounding exercises you can draw on? Breathing, self-talk, simple observations of what's around you? Do you have any friends you can confide in, who can stay with you when you need them? Again in hindsight I think I needed to understand that I had limits, and not get mad at myself for that. Sometimes you just aren't up to going to that class, hanging out in that part of campus, doing that assignment right now, etc. Sometimes its better to just take some time out for your health and apply for marking consideration (or whatever you guys call it in America). I used to treat myself a lot too... if I was having a crappy day, I'd buy a coffee or chocolate and enjoy it in the sun, or go lie on the grass and relax instead of studying during breaks (if there's somewhere around your campus your abuser would never bother to go, and that doesn't remind you of them... easier said than done I know).
