This is what happens when you let things slide and hope people will get hints.

If, the first time he ever touched you, you had pulled back as though you had been burned, and then said

Oh! Sorry, no offense, I don't want anyone touching me ever. It's just my thing.

He would have learned this about you and known it wasn't him - because you just met. But now he's been doing this for 6 years and from his point of view, you have never objected, and suddenly you're going to tell him he's wrong and he's been wrong all this time? That's going to be hard for him.

Here's what I suggest. Next time he touches you, pull back and say "Please don't." He will probably be puzzled and say "please don't what?" Then you can say

Oh, sorry, I have a really hard time with being touched in a business context. Normally I can put up with it because I know people mean well, but I am having a rough day today and that slipped out. But now that we're talking about it, yeah, I actually can't stand being touched in the office at all. I'm sorry, this is about me, not you, but that's how it is.

Now he may or may not lower the rate at which he touches you. But you haven't said "I have hated this for 6 months and you should have known from my responses" or the like, which should minimize the upset to him, yet at the same time you have very clearly given him the information you want him to have.

If he touches you again later, you can remind him "remember what we talked about? That's actually really hard for me" and he should eventually learn not to.

This is what happens when you let things slide and hope people will get hints.

If, the first time he ever touched you, you had pulled back as though you had been burned, and then said

Oh! Sorry, no offense, I don't want anyone touching me ever. It's just my thing.

He would have learned this about you and known it wasn't him - because you just met. But now he's been doing this for 6 months and from his point of view, you have never objected, and suddenly you're going to tell him he's wrong and he's been wrong all this time? That's going to be hard for him.

Here's what I suggest. Next time he touches you, pull back and say "Please don't." He will probably be puzzled and say "please don't what?" Then you can say

Oh, sorry, I have a really hard time with being touched in a business context. Normally I can put up with it because I know people mean well, but I am having a rough day today and that slipped out. But now that we're talking about it, yeah, I actually can't stand being touched in the office at all. I'm sorry, this is about me, not you, but that's how it is.

Now he may or may not lower the rate at which he touches you. But you haven't said "I have hated this for 6 months and you should have known from my responses" or the like, which should minimize the upset to him, yet at the same time you have very clearly given him the information you want him to have.

If he touches you again later, you can remind him "remember what we talked about? That's actually really hard for me" and he should eventually learn not to.