It's just for a couple more weeks, right?
Honestly, I would just focus on portion size and exercise right now if I were you. You could use this time to try to get better acquainted with what your body tells you -- for example, eat slowly and focus on how you feel as you eat, how your body tells you when you're full before you're stuffed.
If you do have some healthy choices, try to maximize them. If there's a good fresh veggie with dinner, try to eat more of that, and eat it first, so you can have less of the more-caloric entree, and not fill up on it.
Will your parents really not work with you a little? What if you say, "Can we have just one kind of steamed veggie with dinner each night? If you buy it, I will prep it and cook it." I can't imagine a parent saying, "No, we will not get you broccoli. We refuse to buy you carrots or green beans." (unless it's not financially possible).
I know you say you are using excuses, but it seems to me you are persevering in the face of many obstacles. I think you grow stronger every day. I hope when you come back to the states you have more freedom and support in your day-to-day living situation.

