"I am a sahm at the moment but I really don't like ironing and nor does he am I right to refuse as he wears it, he irons it or is this just part of my role as a sahm?"
You and your husband have two small children and another due in October. You stay at home to raise the children, this is your main contribution. He works outside the home to provide the household income, that is his main contribution. Domestic chores - a.k.a. 'housework' are a shared responsibility. So no, ironing is no more "just part of my role as a sahm?" than it is 'just part of his role as a WOHD'. It is shared.
By being at home, you have the opportunity to attend to domestic chores when your time is not taken up with childcare. When he comes home from work, both of you have the opportunity to attend to domestic chores equally.
I'm spelling this all out because too many people fall into the wife-does-everything-whilst-husband-sits-on-his-arse-all-evening all too easily. After all, many of us will have grown up with that behaviour being modelled by parents or grandparents (or TV). So I'd first be asking myself, does your husband expect you to be the one to iron his shirts because he values his earning the household income more than he values your raising of your/his children? Does he actually shoulder his share of the domestic chores, or does he expect you to do everything?
Next thing I'd be asking myself is, does the ironing of his shirts fall into being a domestic chore? It could be argued that it does, but equally it could be argued that it is a personal chore, since the shirts are purely his and no-one else's.
Personally, I think I'd be telling him that the ironing of his own clothes is his responsibility. You are performing the domestic chore of laundering his clothes, he prefers ironed clothes so that task should rightly fall to him.
"I haven't ironed dh shirts in about a year since I told him I was not going to do it.
The ironing pile has grown over the past year and dh is complaining he has no clothes and he keeps asking for them to be ironed and nothings been ironed in a year."
I must say this intrigues me. Either, he's been wearing unironed clothes for a year, or, he's been ironing his clothes. Either way, I'd be telling him to just continue how he has been for the past year, but drop the complaining. He can either iron his clothes, or not. But either way, it's not your problem and you don't want to hear about it again.
"The ironing pile has grown over the past year"
That's something I'd probably be changing. I wouldn't be creating a pile in the first place. I'd be putting clean clothing away, into drawers and hanging in the wardrobe. I wouldn't be leaving it in a pile/basket in the first place.
By the way, I'm saying all this as someone who irons. I even quite enjoy ironing! I can perfectly understand hating doing it, but then you make adjustments, don't you? You buy clothes that don't need ironing. Does he do that?