I had 3 children, I took care of them by myself, iit was not easy, I was fatter after 3 kids. When my 3rd child is 2, I started working out, go to family fitness,hire a personal trainer, I lost 15 pounds, not much, but I kept that way for 10 years.
You can do it, too, since you are still young, you will have plenty of time to exercise and be pretty, give yourself some time, don't worry, you are little too anxious. There will be plenty of time to lose weight, your children will not remain young,they will grow up, they will be independent one day, and you will miss the time they are close to you. Trust me, I speak from my personal experiences, my older son went to college, I miss himso much, I miss the time when he was a baby. So mm, enjoy them while they are young.