Why does she say this

[Lithium2020]

I'm in the kitchen, I'm standing by the counter looking for something to eat and I am stood next to the kettle. DW comes in, been wfh and comes down from study.

DW - do you want a coffee?
Me - ummm yea
short pause
Me - actually can I have a tea
DW - "Well make it yourself, you're stood next to the kettle so do it yourself. And I will have a coffee"
Me ... silence.. and then make the drinks

We've had counselling - she was told that she needs to work on her "delivery". I just don't understand why she talks to me like that... I feel so small.

I'm I in the wrong for being too sensitive? Will she ever change. For years I just let it pass me by, then a while back I started being a bit more assertive but its caused friction

My first thought is that I'm not good enough

That is the entirety of your problem. Have a read about validation. In relationships, and self validation.

It sounds like every time she speaks, she invalidates you. Sometimes, we meet people like that, and that's fine. People do what they do. The problem comes with when we either agree with them, or let their opinion be more important to us than our own.

But being a young male, its very hard to admit to myself I am in this position. I feel weak and ashamed

You are being enormously strong to be discussing this, and you can feel proud of yourself for doing so. This is the perfect example of self (in)validation; are you going to see your need to fix this problem as valid, or are you going to invalidate it by calling yourself unpleasant names like weak, and having unpleasant emotions like shame. The choice is yours.