AIO for wanting to call in sick and feeling over-worked?

So I work in a department store, and I tint and sell paint (as well as decking oil and spray cans). Right now its summer, so its really busy. I'd say I get an average of maybe four customers per six minutes. Of course I also have to put stock away, and we're getting a lot of stock at a time to compensate for the busy summer season. Tinting paint can be a long process, especially if I'm color-matching, where I examine samples and try to recreate those colors from scratch.

I think that we're severely short staffed. We have one person starting at 6:30 in the morning, one person at 10:30 (me) and another at 12:30. But because we're so short staffed throughout the entire store, the 12:30 person is usually pulled elsewhere. Because the 6:30 person finishes at 3:00, I'm alone for four hours; the remainder of my entire shift.

Between customer service and stock, I find that I dont even have moments to stop and breath. I've had to skip breaks multiple times because there's been just too many customers to leave. Its exhausting. Now, I'd say I'm a fairly strong guy, but today I felt physically weak from exhaustion; normally I can lift 10L paint buckets with ease but today I struggled quite a lot.

I was quite annoyed today especially, because I had literally just finished up with a customer and then a supervisor (not mine, by the way) saw me standing still at the counter and she said that I "dont have time to relax, because there's stock to put away." They were also the same supervisor to took the aforementioned 12:30 person away from paint earlier (them taking one of us away is very common).

Later, I see them at another desk, literally just chatting and laughing while I'm in the aisle doing work.

Its just a really frustating week and I wanna call in.