Firstly, congratulations for surviving cancer!
Second, I think that motivation comes from setting mini-goals (and a long-term goal) that are realistic and achievable. For me, my exercise isn't heavy and I only do a 30 minute walk with a 2 minute run. Minus the run, the 30 minutes combined with my reduced calorie intake are enough to have my weight falling. It's not incredibly fast (my PCOS doesn't help with that!) but it is enough to encourage me to get off the couch and go outside.
Another thing that works for me is walking instead of driving. If possible, try parking your car further away from work or taking the stairs. Maybe taking the bus part way and walking the rest is easier? Does cooking meals take up potential exercise time? Maybe you could try making meals the night before and reheating them? Are there chair exercises you could do or DVD/Youtube workouts you could try? (Sorry if I'm going overboard with my suggestions!)
What we choose to eat is a huge factor in weight loss. The only reason we gain weight is because we aren't burning the extra calories/energy we consume over a 24 hour period (you probably already know this!) Choosing sugar-free products help too. I love my sugar-free hot chocolate
What motivated you to workout before you gained weight? I think that losing weight is mostly a mental game and it gets easier once you move past the first hurdle. You'll get there!