Starting over

I would love to lose at least 40lbs. I am 56 years old and have a lot of fat
Especially around my stomach. During the winter I don't get much excercise. Last august I have up a stressful job working a lot of hours and feeling exhausted by the end of the week. I was out of work in august so I walked my dog around my bloc and felt good but still very tired at times. I also have high blood pressure and liver disease. I work part time now and feel physically much better but it still is hard for me to get motivated to exercise. I did go to the mall and walk around just to get out of the cold temps. Not very often. Stuck in a rut.