Have name changed because if DH is being reasonable, then I don't want to look like an idiot 
DH went on a night out the other evening with some people from work- another man and two women.
I was away for a few nights so no idea when he got back etc. I was glad he was going out though because he hasn't done anything very social for ages.
This morning went on our computer to check my facebook, didn't realise it was logged in as him. Saw I had a new private message so went to have a look. This is when I realised it was his facebook account, but curiosity got the better of me and I kept reading anyway.
At 3am when he got in from the night out he has messaged her 'hope you have fun at work in 4 hours while I lie in bed'
She later replied 'I hate you lol xxx'
And the conversation continued a bit.
It has made me feel a bit weird and I don't know why. There is nothing wrong with enjoying the company of other people and having jokes with them and sending them messages etc. He is quite entitled to be friends with whoever he wishes. So why do I feel so strange about it?
He had said to me that everyone bar him had to be at work really early the morning after. So why didn't he send everyone an email? Why just this lady?
Am I being ridiculous? I don't know why I feel so weird about it...it's only a message FGS!