I agree with PP above who says you’ve seen yourself through another lens and perhaps you aren’t overly happy with what you’ve seen.
Buying secondhand or high street clothes is absolutely fine, supermarket brands are fine, there’s no problem not buying designer and it doesn’t make you a better person for having designer either.
So I do think you need to separate out the “designer” thing and perhaps focus more on wanting to feel different and make more of an effort with your style?
If your only concern before was does it fit and do I like it them I guess you were not overly bothered about your cohesive “look” or style, and you know what? That’s absolutely fine too. Our outwards appearance is totally irrelevant to some people and it’s all about comfort and happiness in their own self. Whilst others feel joy and happiness in putting effort into their style and enjoy the process of style and fashion etc.
You don’t have to spend lots of money to feel good and enjoy fashion or clothes.
Equally you don’t have to restrict yourself to cheaper labels because it might seem frivolous to others (your friends for example) to spend money on designer items.
Essentially you need to understand WHY you are craving something you’ve never been bothered about before and work out is it just the feeling of having designer brands and the social label that goes with it that you like or have you realised that you can make a bit more of an effort with appearance and do enjoy it?
Ultimately if you work and can afford the things you like then do it, just as long as it comes from a place of enjoyment and happiness in yourself - not from a “keeping up with the jones’” position.
Also, buying preloved is a great way of picking up designer labels and is FAR more sustainable and ethical than buying new fast fashion / high street items.
Try vinted / depop etc