im exhausted

Our store is severely understaffed and are still trying to lower the hours of the staff already working. Because of this, our online department's responsibilities have fallen on me and a few other supervisors due to our manager being on maternity leave and our stand in manager also on leave for a few months. We do not have a manager to report to. A few other pickers and supervisors are on leave at the same time. The ratio of the amount of online orders we get (over a 100) to the amount of people available to work is so uneven. There is usually one or two supervisors working a day which means every responsibility falls on these supervisors. Monday was when I reached my limit to work as I had been working 10 hours straight with only one break and so has the other supervisor who ended up working 13 hours with no second break. I decided to think of my wellbeing and walk out at the 10 hour mark as my body was shaking from exhaustion, hunger and anger. I felt so used. These hours were not even our contracted hours but we had to as every window was full with so many orders and customers coming to collect them. We kept reaching out to the store manager who never helped us but only supplied with one or two members from other departments to pick only one order each which barely helped. He stated that the online windows will not be shut due to constant shutting of these windows which I understand, however this shows that there is an undermining problem that has to be addressed and solved. Prior to this day, I had been working long uncontracted hours and Monday just happened to be the last day I could keep going. I have not been to work since as I feel so exhausted both mentally and physically and I'm dreading my next shift at work already. I feel the need to report this to someone in the headquarters just so some action might be taken to combat the poor management in this store but I have had no luck.

Edit: I must highlight that I work at the NZ woolies however looks like Aussie woolies go through the same bullshit (makes sense, same corporation). Thankyou for all the insight and advice - will be sure to do what i can only for what i get paid and in the mean time, look for new jobs x