I like to avoid getting all tangled up in terminology (affair, cheat etc) and try to keep the focus on whats, right, fair, healthy & wise.
1>Nothing cuts the legs out from under a relationship (ANY) like lack of trust.
2>Trust is built through honesty & openness
Does what I am doing (or considering) meet at least these two conditions ?
If not - maybe I need to backup and rethink.
Because, quite simply, if and when the lack of #2 ever surfaces-comes to light- it has no option but to ripple back up the tree to # 1 . Trust is weakened. And that''s a REALLY slow healing wound which some never recover from.
My thoughts anyway............