Reese Witherspoon was "deliriously tired" and "cried" when she was "working 14 to 17 hour" days as a single mom .

In a post on Instagram, Reese, 49, shared a series of pictures of her with her children when they were younger and admitted it was "really hard sometimes".

She wrote: "Someone asked me what raising three kids and building a career in Hollywood looked like ...

"It looked like spending a lot of time in trailers together ... It looked like always being on the road together ... It looked like my kids constantly giving me career advice! ... It looked really hard sometimes ... "

She added: "I'd cry working 14 to 17 hours, sometimes all night long and still woke up early for carpool. I was deliriously tired.

"It looked like trying to say something positive about work when I got home at night. So my kids would know that my work was meaningful to me and could be fun!"

Reese - who also has 12-year-old Tennessee with second ex-husband Jim Toth - ended her post by declaring the tough times were all worth it, writing: "In conclusion, even though it was challenging at times, having kids gave me perspective about what was important in life.

"Nothing was better than getting to come home and hug them and hear about their day! Grateful to stand alongside other moms in this beautiful, messy journey ... Tag the working mom who needs this."

Reese was in her early 20s when she first became a mom and she previously admitted she was "terrified" about becoming a mother at such a young age.

During an appearance on The Drew Barrymore Show, Reese explained: "To be completely candid, I was terrified ...

"I got pregnant when I was 22 years old, and I didn't know how to balance work and motherhood, you just do it.

"I didn't know if I was going to have steady work, too. I made movies but I hadn't established myself as someone who could demand that it shoot close to my kids' school ...

"I was just like every other mom and dad trying to figure it out. There's a lot of compromise. Every bit of that sacrifice is truly worth it. You feel like that's what makes me wake up on a Sunday, it's not movies or my job, it's my kids."