I have similar issues, have improved a lot but am far from perfect and find it still creeps back up on me if I’m not vigilant
It’s worth picking your battles. I don’t think there is anything wrong with having three tubes of toothpaste in the cupboard unless you mean that you buy three at a time too often and have tens in stock. If that’s the case, try limiting the overall number you allow yourself to have at one time. Reason that even in the worst case scenario, three items will last you weeks/months. Honestly unless you have a cupboard full of extras then I wouldn’t worry about this aspect too much as even some minimalists keep a stock of things that can be used up
It’s the more permanent and useless things that need to be tackled. I assume your university notes are not useful to you anymore. Why are you still keeping them? Is it just a case of never getting around to it, or of being too attached? Exploring these feelings will help you come up with answers which in turn will help you heal and be able to throw them out
Take it one area at a time. It’s tempting to jump from area to area but doing that will make you feel more chaotic and stressed. It will also make it harder to focus on your progress
I’m not a minimalist (yet!) but have found minimalism really helpful with regard to moving on from hoarding. I’d recommend minimalist books / media even if that’s not your goal as it’ll help you change your mindset and relationship with stuff. Personally I’m not a huge fan of Marie Kondo and her method but a lot of people are. I really liked Fumio Sasaki’s book Goodbye, Things. Also Margareta Magnusson’s The Gentle Art of Swedish Death Cleaning. The Minimalists have a Netflix documentary and podcast (not a fan but again, a lot of people are). On YouTube I like A Small Wardrobe, The Messy Minimalist, The Minimal Mom, Darci Isabella. All such different people with different lifestyles, yet they all sing the praises of owning less
If it’s an option and you think you’d benefit, maybe it would be a good idea to look into therapy? I don’t mean to sound dismissive recommending books and YouTubers - my issues are deep rooted and stem from childhood too, so I understand that it’s not that easy. But in the absence of professional help, books and YouTube have had such a positive impact on my mindset