Hi OP. Ok I have some thoughts here based on my own experience and reactions - if these don’t strike a chord in you then feel free to ignore me, but thought it was worth a try.
As others have said, you’re self sabotaging. Let’s unpack that a bit. Where does that impulse come from? Well, you’re at a tricky point in the relationship. Meeting people can be easy enough and then being in a relationship has its own highs and lows but your status at least is clear. What’s tricky is that in between stage when you’ve been dating for a while and are looking to transition into a relationship - you want the security of knowing things are settled, knowing what each other wants, knowing you’re together, and all that. It’s a difficult time, particularly for people who have been single for a long time. Because then being single is your default setting - the easiest thing to do is to go back to what you know, ie. singledom. So while you’re in this transitional stage where you’re building the foundations of a relationship together, your instinct in your head is flipping the ‘feels uncomfortable - emotionally exposed - insecure - default to single’ switch.
Building a relationship is about spending time together, building trust and creating a ‘new normal’. But of course you’re going to feel emotionally exposed and insecure and your self preservation instincts keep itching to pull down the shutters and go back to safety - to singledom. Creating any relationship requires both parties to consciously take a risk of getting hurt, and decide it is worth trying anyway. What you have to decide with this man is whether the potential reward of a relationship is worth the effort of taking an emotional risk, working through this transitional period where you feel emotionally exposed and not quite able to express that fully in the way one can in a committed relationship, and bear with it.
I’m sure there are some cases in which the people involved decided to skip the interim period and go straight to full relationship - and maybe that is a possibility for you too, if for example you decided to just sit the guy down and say ‘I’m really bad with going slowly, I like you, is this serious or not?’. But you may not feel that’s right for the dynamic you two are building together - we can’t know, it’s your call. If you don’t feel you want to try and push things forward, all I would say is that it’s natural to feel the way you’re feeling and if he is a good man then I would urge you to stick with it for a little while and at least see whether any of what I’ve said helps with the roiling maelstrom of emotion and insecurity and desire not to be hurt which it’s natural to be feeling in your position ...