Almost exactly a year ago, I met this guy through a university society and since we both studied the same subject, I agreed to chat and meet him before lectures a few times. He would message me frequently and talk about his social anxiety, amongst other issues, and I tried to help him.
Looking back it was quite obvious where it was going but I had no experience in the relationship department, so when he asked me out one day I panicked and just gave him the vague 'want to stay friends' excuse. I realised this fairly quickly and sent him a proper rejection the next day suggesting we both keep out distance but this turned out to be too late.
Since then he didn't seem to accept anything anyone said. He kept asking when we could talk again, emphasising his struggles with mental illnesses and telling me that he would change if I gave him time. Even after I blocked him, he messaged my friends, dragged in a few of his friends that I knew and repeatedly sent me multiple friend requests using different accounts.
I thought it had died down when the pandemic started in march but I have since found out that he had 'checked in' with my friends every month. Now that university has started again, he is once again trying to reach out to me and I don't know how to deal with it. He is either in denial or does not understand what it means for me to not want to be friends. We have tried to help him with his mental health but he says nothing (but me) helps.
TLDR - I don't want to worsen his mental health but I also don't want to be friends and saying so doesn't seem to register. Is there anything I can even do?