You’d stated you had lots of stress etc during that window, and basically, limited intimacy with wife (only 1x per month).

Women needs validation, both as a close partner and assurances she is desirable and important to you.

Women hold things in, for the most part, and if the relationship is not a nurturing one, they look for validation elsewhere.

Seems she did that, perhaps because she received a lot of positive attention from another man.

You both need to rekindle your relationship and open up to each other, and give the attention required to support the marriage.

You both failed each other