A bit hurt and confused.....

[sasha]

Ive been with my fiance fo 4 years now, towards the end of last year I had an instinct that a women at his work was interested in him, she was newly divorced. He would always tell me that she always talked to him about being so lonely and because i trust him i just warned him to be careful. Ive never hated this woman but at xmas time she told my partner she got a bad vibe from me which I thought that sounded odd. Everything up until now has been good, there has been no mention of the women since she's seeing a few other men on the internet, but over the past few wks its been a bit rocky for me and my partner, he's been stressing as am I so we've been fighting really badly to the point we're one of us almost ups and leaves. He tells me theres something on his mind but he cant tell because he needed to sort it out by himself, we have never really kept any secrets so this kind of hurt that he couldnt tell me. After a few days I asked him if he could tell me, so he sat me down and broke the news that he had been having lunch with this women and asked her out one friday nite when he called me and said he was going out for farewell drinks with workmates, she told him then how she felt about my partner, she just outright said she has feelings for him, his response was that if he wasnt with me he would go out with her but is happy to stay with me. I was and still is very hurt and upset particularly about him lying to me, but I trust that when he told me nothing else happened that, that is true, I dont have the intension to leave. So my question is should I still be hurt and upset, or just get over it and move on?????? He says he's sorry that he lied, and will now (especially that he knows she has those feelings for him) try to avoid her at work but wont completely ignore her which i dont have a problem with. I just dont understand why after I warned him that he initiated all of this. Thanks guys for any advise you can give.