Guys, My boyfriend got angry seemingly out of nowhere and is threatening to break up with me. What is going on?

My boyfriend (29) is one of the sweetest and caring men I've (27) ever met. He's supportive, keeps me positive when things look bleak, and makes me laugh. We're a lot alike and with that, I understand him sometimes but his mood swings are really confusing me.

He works in a hospital and he's gone through some pretty horrific things during this pandemic. Most days, I have to prepare myself for what he'll say when I answer the phone - He's called crying on several occasions because of patients he's had and some that he could not save from COVID-19. With that, plus the 12-16 hour shifts, he's stressed. Way more stressed than I am but I try to support him any way that I can.
Yesterday, I asked him to hop on GTAV with me to do a quick mission (I'm still learning the game) but I couldn't figure out where to go to start the mission. He got mad that I wasted our time but didn't want to hang up our call and didn't want to explain why he was mad. So we both just stayed on the phone until he fell asleep - which I'm kind of laughing about now but?

I texted him some hearts today just to say hello to which he replied that we had to talk about our relationship. And I knew that this was just going to be a breakup threat.

He's done them 2 times before. Where he says "We should just break up." and talks about how I deserve better and how he wants to be a great boyfriend but he can't because he's so stressed with the pandemic. This usually turns into him crying and me reassuring him that he's a great boyfriend (because he is besides these episodes!) He then apologies and says that he didn't mean it.

My question is... why does he do this? I'm aware that he might be depressed but is this something more? Is this bipolar or borderline personality disorder? I can't get this out of my head. He hasn't spoken to me all day and frankly, I'm just planning on giving him space until he calms down at whatever he's actually mad at.
Guys, My boyfriend got angry seemingly out of nowhere and is threatening to break up with me. What is going on?
Post Opinion