Good news is you are here early. Don't pursue a reason. If there is an affair you will find out. Really think back to what issues you had. Did she ever reach out to you about working on issues and they got swept under the rug ? It could have been quick, possible multiple times, but not addressing them could mean things seemed good but were not.
Typically either lingering issues and something or someone triggers them to BD. Not necessarily an affair, but always a possibility. Keep your eyes open there, but don't let that kill you right now.
You will struggle, but you WILL figure this out as nuts as it is right now, but patience and space is key. Validating her (even if you don't agree) will lead to answers.
