Generally,if the exam boards are informed about your circumstances, even if psychological, they will be sympathetic and give you some sort of advantage.Furthermore, if Unis have proof of the events that led to you becoming psychologically distressed they may even give you a bit if leeway and lower your offers.
It all depends on the circumstances, I'm so sorry to hear about your situation. I can ask my careers teacher more about this and give you a clearer answer, but you should act quick on this, even if it is just emailing the exam board.
Don't feel as if you are overreacting because many people have gone through tough times before their exams and many exam boards have had to help them out, so it wont be anything new to them.