I'm in the exact same boat! Minus the fiance thing, I don't even have a boyfriend.
haha.
I just graduated, moved back home to my parents, and started a brand new teaching job. Life is insane, so many changes to take on at once - and it's been tough, I"m not going to lie. I had my life in control before, I didnt' need daily planning, I was able to be in control of my schedule and food just natural based on the habits and schedule that I created for myselfe. But now, I have to plan every single detail and calorie in order to manage the changes that have occurred.
I've managed by over planing and being in major control of everything. I can't just let things crop up now, which stinks. I plan out my meals before hand - my entire schedule for the day, when I'm going to work out - and for how long. Once this routine becomes comfortable again, I won't have to plan so much.
But that's how I'm dealing. And, I told my family about what the deal is. I may be buying my own food, I told them not to be offended if I dont' eat with them. They agreed to let me cook healthy meals 3 days a week. Most of my family is pretty unhealthy. So it's a big thing that they're letting me cook!
So good luck - just use the supports you have around you, whatever that may be. 3fc, family, friendly, fiance, journals, whatever you can do to get comfortable. GOOD LUCK!