Congrats on starting nursing school (and all of your other successes)!
My main advice is: plan ahead!
I'm a student as well, and it's just amazing how much harder it is to eat well on such a crazy schedule that changes day by day. I lost so much more weight at a constant pace the year between programs when I was working 9-5, always went to the gym after, etc....now I still am losing...well, when it's not finals and I go AWOL from eating well and exercising
...but it just takes more effort and willpower. It can be tough to decide between going to the gym and studying for an exam...I still feel like I haven't really found a solid solution--it's amazing how few healthy choices there are on campus--other than just thinking ahead of how my day looks and what/where/when I'll eat. BUT, you *can* and you *will* do it...it's much easier when you've already established healthy eating patterns and choices.
Also, carry snacks (part of planning ahead), especially since it's sometimes hard to find something healthy when you're hungry...I'm follow South Beach, so for me that means high protein snacks such as string cheese, apples, small cans of chick peas, etc. Also early on just scope out places near your classes etc. that you can get you-friendly snacks/food...
Even the eating terribly during exams thing isn't necessary...I ate fairly well and was even avoiding most caffeine for most of the semester through midterms (all hard science courses, too!), and survived...I just let myself cave these last few weeks but even at the same time *knew* that I'd actually feel better if I made healthier choices...
On the bright side, you might find yourself so thoroughly occupied by school and family that food becomes less of an issue (if you're a boredom-sort of eater, as I can be...)