Congratulations on coming to the end of your chemo treatment, flu! That is wonderful news. 🙂
Lots of good advice here, but I especially like what OCR, Jazzman, and exsdgal wrote. Go slowly. Most people who lose weight quickly gain it back, and more, just as quickly. It’s a lifestyle change, not a diet and exercise program, so enjoy whatever it is that you eat and do. If not, any success will be short-lived.
Enjoy this new phase of your life! You deserve it after all you’ve been through.