I wouldn’t call being upset and angry about the consequences of his infidelity “bitterness” (apologies if I already posted a similar comment here, but I think it bears repeating, especially with the prevailing cultural narratives around cheating that tend to favour - mostly the males - perps). I’d call it righteous anger for being put in a position where divorce was even something you’d consider. The whole thing is unfair on you (because none of it, aside from initiating divorce as a consequence of his choices, was your choice) and you’re entitled to be angry about it.