Look, it was cruel to say that to him.
I can imagine if my dp said something similar, it would break something inside me, tbh. Particularly if I had been supportive, and he wasn't seeing it and then said something like that. I would feel like a psychiatric nurse trying to talk down someone who didnt care how I felt, rather than a partner to someone, iyswim. And I might just feel, you know, I'm struggling too and I cant cope with this, I'm out of here. I don't think that is unreasonable - I think you see that and that is what hurts.
What happened to your relationship wasn't nice at all. What we are going through as a society right now is v v destructive. There are and will be casualties, and sadly it sounds like your relationship was one of them.
Its shit. That's an understatement. Its absolutely horrible. Of course you feel horrible. A dreadful thing has happened, a loss, and if this horrible virus wasn't here, maybe it could have been avoided. That hurts too - the randomness of it is doubly cruel.
You've had good advice on taking it minute by minute. Can I suggest writing down how you feel, as well. Over and over if need be. You will find sense in what has happened- it takes time but you will get there. You can and will survive this terrible event. I know that because I have also been there, more than once. I really do understand 