I mean for me nihilism is a perspective that I have in general, i.e. there is no purpose to anything really in the grand scheme of things. But when that also means that you can't find personal joy in anything, I think that becomes a depression thing. I have also been in that position and after a lot of therapy I realised it was because I was so burnt out on doing what people wanted me to because I was 'supposed' to rather than actually asking myself what gave me enjoyment if you took everything else out of the equation. It took me a while to realise what I actually personally cared about because I've spent so much of my life masking basically.