Have you spent any substantial time in your life being single, @NC1769456? It's the best way to learn how to respond effectively to your own emotions, without someone else's interfering.
He literally begged me saying that he was going to fail without me. I didn't know what to say so just hung up and blocked her number. It's a lot. I don't know why he won't leave me alone, when I've made it so clear that I can't do this and also why I can't
He's doing this because his mindset is toxic. If his life falls to pieces around him, he'll have to admit that he has a problem. You are an integral part of the 'brave face' he puts out to the world. 'Hey, it can't be that bad, or my partner would have left me, right??' The key thing to recognise here is that he is TOTALLY dismissing your feelings, even when you've stated them to him clearly.
And that's all you need to do to validate yourself. In all situations; work, relationships, family, choosing a counsellor, everything. You say clearly how you feel, you get the response, and you see how you feel about the response. If you feel bad about it, you create emotional (if not physical) distance. If you feel good about it, you create proximity. It's a filtering mechanism that lots of people are taught instinctively by non-toxic parents. You didn't get taught. (nor did I) But luckily it's learnable.
If you want to know what's wrong with you, that's it. You didn't get taught a simple mechanism when you were growing up. You can learn it now.
I went to brilliant counselling for a year, and what it made me realise is that I had never needed counselling. There was never anything wrong with me. The belief that something is wrong with you is what creates the poor relationships, because you are more ready to blame yourself or feel you deserve to be treated poorly than you are to respond to how you feel as per what I wrote above.
I really hope this helps. I hope you get the little kernel of information you need that will make the penny drop. It's a different thing for everybody, but you can free yourself of the negative self judgement right now if you find it. I found great relief in not being 'special'. I always thought I was a bit weird, a bit different. A bit faulty. But I'm exactly like everybody else, and so are you. (except for the individual things we have that make us fabulous, obviously
)