Imagine if you will

[worriedaboutstuff]

Your dh works in a field loosely affiliated with skiing for example, you have asked if he will take you dry slope skiing as you have never done it.
It is not something he has ever done and he isn't keen, so you think nothing more of it.
He meets someone at work really into dry slope skiing and sends her a text asking if she wants to go.
What the fuck do I do now?

Ask him wtf?

That is totally unacceptable. I would be making that very clear as a first step.

How did you find out about the text?

I found it by snooping I'm ashamed to say.
He'd been talking about someone at work, I have already asked if something is going on, he says no.
I can't find anything else but I am distraught.

I have no exit strategy, I am a sahm with no job.

I don't think I am stong enough to pretend, I am shaking and have been sick.

When is it taking place? I'd keep quiet and then turn up and surprise them.

I don't know that it is taking place. It is something that needs to be booked quite some time in advance and could also be done as a work related thing.

He's self employed, I have no access to his personal financial stuff, it's at his office.
I don't think he has actually done anything but at best I think he has an infatuation with this person.
I feel crushed, it's ridiculous.

Whether or not anything has happened yet, there are plenty of red flags here to show that it easily could develop if left unchecked.

I would confront him with two words "I know" then shut up. His reaction will speak volumes.

That's the thing Itcouldbeworse
I have a feeling I have caught him in time as you say, but I just can't seem to get past the fact he has made me have trust issues.
I don't want to be one of those women who spends the rest of my life being paranoid.
It's hard, because we have been through so much and I adore him.

Thanks for your advice, I'm going to go and get a shower and get myself together.
Quite how I'll handle myself when he gets back from work I don't know.

This is one of those situations where, difficult though it is, you have to have the courage of your convictions and confront him with what you know. 'Never mind how I know.... I'm pissed off that Beryl at work gets the skiing invitation and I'm given the cold shoulder.... deal with it'

Your SAHM status appears to have knocked your confidence and led you to believe you are vulnerable. If you do nothing else, suggest you a) get back in the workplace a.s.a.p. and b) have half an hour with a solicitor to find out your rights in the event of a split.

Yes Cog me being a sahm has knocked my confidence. I'm low at the moment anyway as our child is ill, so I'm feeling particularly fragile.

I don't really have grounds to split though really do I?
Can't exactly go to a solicitor and say I want a divorce because my dh wants to ski with a woman who isn't me?

Fess up and say ' When you take whatsername dry slope skiing, may I come too.please '

Perhaps as you spend a lot of time already together he fancied spending it with someone else this could easily have happened with a male friend. Whilst it is understandably very hurtful you shouldn't rush to conclusions.
Sounds like you're both facing a lot of stress so try to nip it in the bud but address a mutual need for relaxation time. He is probably looking for escapism but is perhaps seeking an illegitimate route.