Getting back on the wagon-HELP!

Guys, the past five days have been brutal! I guess my official excuse is birthday/exams but STILL. I really want to get healthier and it's frustrating me that I keep falling off the wagon. I'm starting to lose hope in this already. I'll try to eat healthy but then my parent's will order out for dinner or like, I'll eat a bunch of snacks as dinner and then my family turns around, makes dinner and expects me to eat it. I know in the end the responsibility falls on me, but it's getting discouraging. Any suggestions as to what to do?

Thanks
-Prin