The good news is that a weight loss/get healthy program is *exactly* what you need for self-esteem. IOW, what you are now going to start doing is something great for yourself, and you deserve it.
If you approach it that way, if you remind yourself that every single thing you do from now on is FOR you, for the great person you really are, you will find it easy to stick with it. And the feedback loop will be positive -- as you lose weight, as you feel better and better physically, you will reward yourself by doing all the right things.
I know what it's like to have that weight creep up on you and you don't know how it happened, but I'll tell you what's most likely -- you got bamboozled by the food makers and fast food providers who wanted to make a profit (and cheap food is nearly always BAD food, in terms of calories and nutrition). You ate things that were easy and inexpensive and they were all the wrong things. Turning it around will require you to be a lot smarter about your food choices (but you're a smart person or you wouldn't be in nursing school).
So... start studying just as hard about food as you do in school. Learn what's right to eat, and you'll be well on the road to total physical health (and looking good). Remember that someone in the profession you have chosen is too valuable to lose -- we need you more than ever (particularly us old people :>) -- and before you can care for others you have to start caring for yourself.
Here are some rules to get started (and you can find the rest here or on the net -- if you have any troubles keep posting and asking questions):
1. Cut out ALL sugary drinks, including fruit drinks. Diet sodas if you must, but even those aren't the best (best are unsweetened tea, coffee and, of course, water).
2. Eat five or six meals a day and NEVER skip any. You heard me -- don't think you are losing weight by not eating, because skipping eating every three hours just shuts off your furnace. And breakfast is by far the most important meal of the day -- you HAVE to eat within 30 minutes of getting up, and make sure you get at least 30 grams of protein.
3. Vastly reduce or eliminate all simple carbs -- white bread, candy, cake, you know what it is because it's all crap. If you need sweets, eat fruit (but not fruit drinks). Stick with this for a month and soon fruit will seem so sweet to you you won't need much to feel satisfied.
4. Get some exercise, and definitely some strength training. By that I mean you don't have to lift heavy weights (my wife doesn't) but at least do some squats and pushups (do modified ones as even the weakest woman can do them). Get cardio at least three days a week but don't kill yourself -- 20-40 minutes will do, and even walking is good. But it needs to be FUN because this is a journey you'll be on the rest of your life, so if you don't like walking/biking/spinning find something you DO like (a sport of some sort, like tennis, would be ideal).
All of this should get you going but if you're not losing at least a pound a week (ideally) then you need to start counting calories. You don't have to do it the rest of your life (although you might) but if the weight isn't coming off make sure you do it religiously for at least a month. You can find the formulas here or online for your target weight but the important thing is to NEVER feel hungry (by eating five or six times a day you won't). Again, this is what you are going to do the rest of your life, not just temporarily. The good news is once you get going it will make you feel and look so much better you'll be excited and happy to do it.
Good luck to you! I know you'll make it (and I'm looking forward to having you, or someone like you, take care of me into my old age).