Had I not been born, I wouldn't know the difference, because I wouldn't exist. That I do exist now is irrelevant, because we're talking about a hypothetical universe where that's not the case. Not being born is a fundamentally different sort of thing than being alive and then dying. (If it wasn't, everyone who can physically have a child and isn't doing so right now would be committing murder.)

Everyone involved would've been objectively better off had I not been born. Both of my parents would have been happier. Everyone around them who had to deal with the fallout would be happier.

To be absolutely clear, this is not an expression of any sort of guilt on my part - I had no input into this terrible decision, and I take no responsibility for it. But any observer would have called it an obviously bad idea, if they didn't have to dance around the psychological and social implications of saying that within earshot of the child. One of the benefits of being an adult with a fully formed brain is that I can now look at such hypotheticals objectively, without conflating them with my own self-worth.

So my past, as terrible as it was, is a sunk cost. If I spontaneously died right now, it wouldn't undo any of that, nor make me or anyone else happier. The best I can do with the situation I am currently in is to keep living, and try not to repeat the mistakes of others.