Try to take it one minute at a time. Distract yourself. Do something innovative...text someone else, maybe your wife or friend each time she calls. If you are able (and this is almost impossible for me..but I've tried)...maybe for a few hours put your phone in a drawer, where you cannot see it or hear it. Come to DS and read the boards.....
We totally understand those triggers.

Block her tonight while you feel strong.

You have come this far with NC I would see it through. Let me give you another motivator. Aside from the hurt and pain I have caused my W due to my A, there is collatoral damage as well. I was thinking this morning, sadly that my kids know, and will never see there Dad the same way again. Never...
Given what you have said about OW, I don't think this will be easy. I know your hell and you have a great opportunity to start climbing out of it. At this point I will be blunt: Don't fuck this up!

Spontaneously call you wife and ask her "out"

listen to pinkpony!

just block her - problem solved!

Well she called a few times yesterday, but I did not answer. She left voice-mails asking me to please call her back. Today no calls and I found myself kind of missing the attention (it was late afternoon and I was tired from working all day). I took a walk and went to gym and went home without contacting her at all. I am a little sad because after over two years I have developed feelings for her and don't want to hurt her. The good thing is that after a good nights sleep, I always have more clarity in the morning.

I actually put the phone away in a back pack and didn't look at it until late in the day.

Yes you have feelings and don't want to hurt her, but you simply have to overcome that. She will survive and probably one day be so glad you had the courage to do what she could not. Remember... NO you cannot just be friends.

The calls will keep coming, they will range from pleading, desperate, logical, friendly. Unless you have some unfinished business that MUST require contact, you need to cal your phone provider as I did and block her. Once that is done, do it in your phone settings. Finally, turn phone off and back on. You make think this is much but it's important. You do not need to be listening to her messages. They will wear you down.
Btw.. I will advise carefully here... I am assuming you guys have had recent conversation that you want to end it or she at least knows you are not just pissed off or playing with her.. If not send her a message that leaves her with no doubt it's over.. Tell her she is not to contact you whatsoever. A hint that the W maybe behind this deascion can be a good thing. Wait for her to respond, acknowledge her response, and tell her you are blockin her.. She needs to know you blocked her and you don't need the thought of messages waiting on you to answer. Sounds brutal but it is for your own good... And hers.

Some more:

Establish self talk,defiant type talk ..
When you do think of her think of all the bad things
Stay away from anywhere she could be.. Like FB and do not fish around checking up on her. It will only set you back.
When you want to contact her.. Call/message wife.
Be prepared to be emotional .. W may want to know what's up.. Idk. Allergy season.
Hang in there and nothing wrong with leaning on us..