Rumer Willis has an "unknown stomach problem" which has left her sick for "almost an entire month".

The 30-year-old actress has said she's been feeling under the weather for the majority of August thanks to a mysterious illness which makes her feel as though her "stomach is on fire".

In a lengthy Instagram post on Thursday (15.08.19), the 'How Do We Let Go?' actress wrote: "This was me yesterday. Exhausted, Overwhelmed and Broken Down. I had just gotten off the phone with my sister after having a full little kid meltdown. Sobbing about how I was so tired and feeling helpless. I have been sick almost the entire month of August that started with food poisoning to then an unknown stomach problem where I haven't been able to eat because when I do it feels like my stomach is on fire to the flu that turned into a sinus infection. I felt helpless and scared and so utterly overwhelmed. I felt like time was just drifting by and I was trapped in a body that didn't want to work with me. (sic)"

Rumer went on to say she's been trying to "listen" to her body and have "some compassionate self forgiveness", and is thankfully starting to feel "a little better".

She continued: "I have been in so much pain and kept trying to fight it and be angry and sad, but what I realized was that I was trying to control it. I was listening to my body or what it needed and was just trying to control how I felt and when I felt it. I did some compassionate self forgiveness for any judgements I was holding against myself or my body for not behaving the was I wanted it to and really just allowed myself to be exactly where I was at and let go. And I woke up this morning feeling a little better and feeling much more integrated in myself because I was no longer at war within. I am by no means 100% yet but getting there. (sic)"

And the 'Once Upon a Time in Hollywood' star felt compelled to share her illness story, as she wants to prove to people that everyone goes through "tough" times.

Closing off her post, she wrote: "I wanted to share this because I think it's important for me to share not just the fun great parts of my life but also the tough ones too because we are all just doing the best we can with the tools we have. It's my birthday tomorrow and i wanted to start my new year letting go of mindsets, beliefs and old stories that no longer serve me. So I encourage you as you move forward with you day, week or even month allow yourself to let go of the control of the outcome, control of the expectations of how it should go or look, and let go of whatever story you are making up about yourself if it doesn't turn out the way you planned. It's all happening for you not to you.... Anyway for any that this resonates I hope it helped and if it's not for you love to you anyway. Thank you for allowing me to share myself. (sic)"