How do you exercise with a four month old?? Before I got pregnant, I walked an average of six hours…

How do you exercise with a four month old?? Before I got pregnant, I walked an average of six hours a day. I don't have money to buy equipment nor to get a babysitter. Besides, I hate exercising inside. But it's so difficult to take a baby on a 6+ hour walk! But I have to lose about 100 lbs. (I was on bed rest during pregnancy, then I couldn't walk for months after pregnancy because of blood clot surgery I needed).