Was I out of order?

[nc20144]

I will try not to make this too long.
tonight while trying to install an app on DH tablet a FB message alert popped up from a woman whose name I recognised.

when I was 7 months pg with DD, DH had a work night out, got completely drunk, phoned me by mistake and I heard a lot of commotion in background and a woman telling him to 'get in the car'. when he came home I looked at his phone and there was a text from someone calling him babe. I text back saying whose no is this and reply was 'X' from earlier tonight.
next day I went ballistic. He said nothing happened and she was with a boyfriend. I let it go.
2 weeks later I find a receipt for a (quite expensive) lunch for 2. again, I went mad, he claimed he met her and her BF. He apparently ate nothing and the receipt was from their meal
then a text arrived from OW along the lines of "thinking about u too. hope all is okay but if not would be great to see u"
I phoned OW and she backed the story up but said her BF was out and she'd get him to ring me when he came in.
He didn't and i got a text from her saying she wasn't getting involved in whatever domestic we seemed to he having.
DH swore nothing happened, i had no proof, I let it go even though I knew he was still texting her.
I found her FB page and basically stalked her for months she was 4 or 5 mth pg when they met but was single. eventually I stopped looking but never forgot the incident.
fast forward 4 years to tonight when I find out he is her FB friend. He can't understand why I'm angry and upset. We argued and he got angry that I was talking about something that happened 4 years ago. again proclaimed his innocence. think he was shocked i knew a lot from my FB stalking. He deleted her off FB then said he was deleting FB altogether. said I didn't trust him, I'd ruined his evening etc and sat in silence all evening.
was I out of order?

The 'I would trust you' shows he has not engaged with the question at all and is just telling you to STFU and not ask him difficult questions I think.

I think at the time of the original incident yes, his boundaries were poor. He should never have given out his phone number and certainly shouldn't have been texting OW never mind meeting up.
I think eventually he realised this and this is why the texting/phoning came to an end after a few months.
I should have confronted the issue properly at the time but I was pg then had a new baby. also by the time I could prove his story was BS many months had passed.
to his credit he stopped drinking and is a devoted husband and father. There have been no reasons for me not to trust him in the 4 years since.

I think accepting this OW friend request on fb was pure stupidity and thoughtlessness. I think he was shocked by how angry I was over it.
We are speaking again now but the argument hasn't been mentioned again and probably won't be. I don't think the full truth would ever get told anyway.
He now knows my feelings about this woman and that I didn't swallow his (bad) lies and I know this argument has affected him as he has hardly slept for 2 nights. although he won't admit it I think I've given him a lot to think about and he realises he's treated me badly.
as I said at the start I had no intention of leaving or throwing him out over this so I feel I have to let life move on now.
Thank you for all your advice and support. I feel a lot more at ease with the situation just through talking about it.
If I had known about mumsnet 4 years ago maybe I could have put this to rest then.