You said sex is how you temperature check. Which is unfortunate, b/c It may not be hard for her to go alone with it. And you may misinterpret or project your feelings onto her actions. I assume she knows your method of temperature checking, correct?
I believe all men temp check this way. Does she know it. I have no idea. Could she go along with sex to deceive? Sure, but I doubt that it wouldn't be obvious. WW/WAW are very focused on being true to themselves, IMO. This is one area that she would struggle with a ruse in spite of being true to herself.
With my W? Possible, not probable.
M 53 W 54, M since 98 D15, D19 8/2013 discovered EA, W maintained contact with OM until 10/14 7/2/17 W said she wanted S, 7/25/17 moved out of MBR 12/17 W says moving out 5/18, W still in home.
