How about addressing this in your essay? I think that you should address what happened carefully and write about what you learned. I think in fact, your change of heart could get you into MIT. Do not give up. You are in fact unusual in that you have an interesting record and overcame it very very nicely. Aim high. I think you can make it. ACT of 34 really is good enough for MIT if you have other strengths. Take the national math exam, enter a science fair, and stop worrying. You cannot change your past, do NOT let it define who you are today.