Need serious help and advice ...

I work full time and during christmas party in 2007 i met one of operations director of my company. I spoke to him and found him very humour guys.

due to restructuring, he started to sit with our team as we had few hot desk.

we started to chat on Im but mostly about owrk, job, study so on or travel. after 5 months we went out for dinner and then know that we both like walking. As it was may to Sep, we use to go for walk after work almost 3 times a week as he was only in 3 times in the office.

one day i invited him at home for dinner, we end up sleeping since then. he is married with 3 kids and he doesnt want his wife to know about his having affiar.

we had argument so many times that i dont want to carry on with this. i wanted him to be a frined not having an affiar.

i tried to ignore his calls, ims, emails or tried less interaction with him but dindt owrk.

This year i decided not go out for meal with him or take lift from but failed
after two months, he persuaded me that we can be frinds and let go for dinner. We went and when he dropped he asked me if i can come for coffeee and we end up sleeping together and having sex.. which i managed to avoid for 3 months but happend again.

he will not leave hsi wife as he made very clear ..

What shall i do, it is not possible to leave job..
thanks
nightfall