Before i was pregnant i ate healthy and walked and exercised every day and was very fit

During pregnancy i was pretty sick so could not eat well , i put on a lot of weight but a few days after the birth i lost it all , so it was mostly water weight,but i feel the way i am eating now ill put on heaps of real weight soon
anyway
Now i feel i can eat anything again as i am not sick and i find i am eating not well, eating a lot of junk and easy to cook foods that arent that healthy as i am so tired and sleep deprived etc

I really want to exercise like go for a walk each day and eat better.
how did u do it with a new born ?
any tips from what u did how u manged would be great!!