Welldone for deciding to make the change, I can see how hard it is by being surrounded by food all the time. My partner has decided to join me for my walks, which gives me more motivation to do them daily. I end up doing a combination of walking and jogging which is great for getting the heart rate up and burning more calories from walking that you would burn from the average walk.
I lack motivation also, but I just tell myself "Just a walk for today then, 30 mins or whatever" but once im out... well, may as well start jogging a bit!
Good to hear that your fiance wants to lose some weight as well, that always helps maintain healthy eating. figure out how many calories you should eat in a day and then maybe work out a daily plan for food intake, leaving space for all the sweets that you need to taste throughout the day?
Good luck you'll find what works for you eventually, just have to keep trying different methods.