Seriously consider the gap year idea. I had a really bad year during year 13...and therefore ended up deciding to take a year out. I've spent a year relaxing, working part time, gaining experience in the field I'll eventually be working in...and then went off to Central America with Raleigh International. While there I was offered support of a different kind which helped me to figure out a lot of the past. I've finally come to terms with who I am and whats happened in the past, and the fact it belongs in the past. I'm now super excited about uni because I know I'm strong enough to cope.
Whether youre off to uni immediately, or later, I think its well worth considering talking to someone before stressful situations set in. My plan is to make a visit to the counselling place immediately, explain to them the situation, and then hope I never have to go. The thing is having already gone once the fear relating to getting help, should you need it, should be lessened.
I agree with the fact that although yes, today was a mistake, dont allow it to put all your amazing work at keeping going aside. Youve managed a year, and yes youve self harmed, but once in a year is nothing. It proves that there are still underlying issues, but now you need to consider how to deal with these. What are you going to do next time something gets stressful? Are you going to self harm, or are you going to find a much better solution? I trust that you'll make the right decision.
Give your mum time to calm down, and then go and have a chat. Be honest, explain that you know youve made a mistake but thats all it is. Explain why you did it, and how she can help you in the future. Tell her you got stressed because of the argument, and that next time you would appreciate it if she stepped away before it got to that point, and promise that you will then, when you are up to it, go back and discuss in a much calmer fashion.
Youre mums worried about you, but at least she cares. Let her know that you understand shes scared for you, but that you want to take control and sort everything, show her that you are capable of uni, but be willing to accept it may not be the right decision.
Sorry that this is very very long!