Does it necessarily have to be caused by cheating?
Because there's abuse-related hurt/comfort: http://www.mangago.zone/read-manga/katsubou_no_manazashi/
http://www.mangago.zone/read-manga/shachou_to_hisho_ai_no_shoumei/tr/92834/page/130/
Abandonment-related hurt/comfort:
http://www.mangago.zone/read-manga/doushitemo_furetakunai/
The first story in this:
http://www.mangago.zone/read-manga/amai_nukumori/
http://www.mangago.zone/read-manga/sumanai_masumi_kun/
Even amnesia-related hurt/comfort:
http://www.mangago.zone/read-manga/doubt_nishimura_shuuko/
Along with standard Cheater fic:
http://www.mangago.zone/read-manga/koi_to_wa_yobenai/
Most of the good plots in yaoi have elements of hurt/comfort in them. The trick is to find the ones which stay real, not maudlin. I don't think all the ones in this list qualify.
not yaoi but still worth the read: http://www.mangago.zone/read-manga/holiday_love/
like cheating or something...