I'm sure it does hurt. I see affairs associated with an addiction. You have become dependent upon the needs that are getting met with the OW. There are chemical changes also associated with the affair and how you percieve it. You also go through withdrawl symptoms as well. Only you can decide which relationship is going to get a fair shake. You have spent long time together to toss it aside without giving your marriage an honest chance.
You could learn a lot from reading the different situations on the board. Maybe gain a little bit of insight as to why your wife is fighting for the marriage.