What are some sure fire ways to lose excess belly fat?

I had a baby two years ago, and it seemed okay at first to have this excess belly fat but now that she is TWO YEARS OLD, I have no excuses anymore. I have been doing my daily exercise regime, walking two miles, crunches, push-ups, sit-ups, leg pushes…but I am getting bored with it all, and the results are slow. I also don’t have the money right now to join an expensive gym. Does anyone have any ideas, or any insight from personal experience?