TL;DR: manager unfairly informs me "it's just as easy to hire 3 shift supervisors as it is 2" which results in me bawling like a baby in front of my coworkers. And now i feel a lot less important and way more expendable. Should I confront him or go straight to HR?

I'm a shift at a retail store and there were 2 other shifts and my manager. When i asked and applied to be a shift, my training was sped up due to one of the shifts breaking her leg and a need to be replaced while she recovers. During this time, my manager relies heavily on the other shift and still doesn't teach me much. Flash forward now to about a month ago, one of the shifts put in her 2 weeks notice since she found a better job and the other shift with me got fired for stealing a small sum of money. Which left me and my manager to close and open the store suddenly. He was stressed and i got pressured to fill shoes i honestly hadn't been trained for yet. I regretably don't do well under pressure so I've screwed up during this time it was just my manager and i are working and he decided to inform me that while he looks for more shifts, it's just as easy for him to find 3 shifts as it is 2. Legit, this made me cry after i left the conversation and went back to work. I might of been able to hold it in if my coworkers didn't notice my change in demeanor and ask me what's up and suddenly be real kind and comforting. His talk motivated me to do my job, but i honestly should have commented about his words, right? I feel awkward around him now, like I'm stepping on thin ice all the time and it's stressing me out. I cannot lose this job. Should i try talking to him or should i go straight to HR?