Oh, I understand! It is SO hard to find time for me to exercise too. You are not alone. But it IS a priority to stay in shape so you have to treat it as a priority!
I have 3 kids, ages 10, 8 and almost 4 and I am raising them alone, no sitters , no help. So what we do in the summer, is take a nightly 1 hour walk. This way we ALL get exercise (well, the little one sits in a stroller sometimes). We also park as far as we can from places we go. And I have a portable stepper that I pull out on rainy days and we all take turns.
When they go back to school in 3 weeks, then I can get back into Yoga 3 days a week and cardio the other 2.
I'm sure you can find time to squeeze in , babies nap, kids watch TV, just look for the times you can grab 10 minutes and do it!