I am exactely in your position i live in a diff town then my family, i dont drive and often sit home by myself with my 7 month old son....
For me since im the one making the grocery decisions in the house I just dont buy garbage anymore. My house is full of veggies and fruit and whole wheat and whole grain low fat and low sodium..... this way if I do get hungry for a snack i know its going to be a healthy choice.
I also set aside at least an hr a day to workout. I downloaded a few exercise videos and burnt them now i workout in my livingroom while my son is taking an afternoon nap. I also try to go for a good walk with him at least a couple km`s everyday.. all that plus trying to run around after a 7 month old is a lot of work. lol
My advice probably would be also to get rid of the junk in the house and set up some sort of exercise schedule... youll feel better about everything if you have a schedule and it is working