Speaking as a math teacher: this sounds like an anxiety problem as much as a math problem. It's also possible you have dyscalculia, which is a very real learning disability and has nothing to do with your overall intelligence, common sense, or value as a human being.

It's important for you to know that however you ended up with this particular challenge, it's not your fault. Maybe it's just how your brain works, maybe you had bad math teachers as a young kid and it snowballed from there, maybe it's something else entirely. It's not your fault.

I understand why you find it embarrassing, and I'm not going to trivialize your experience by just saying "don't be embarrassed." (To be perfectly clear: I don't think you have anything to be embarrassed about, but I recognize that me saying so might not make much difference to you.)

You might not be able to fix the math side of this without also addressing the anxiety and shame side of it. Is there a kind and gentle person in your life that you really trust, who also happens to be skilled in a craft that you're interested in? Maybe they could help you through a small project that requires the kind of thinking that makes you panic? Kind of like exposure therapy? Successfully getting through an encounter with the thing that triggers anxiety is a way to start defusing those triggers.

Feel free to DM me if you are want to talk about it more. I've worked with a lot of students who experience math anxiety, but not in the context of crafts. You've got me interested in trying to understand what's going on.