Hi JS, it sounds to me like he's restarted his affair. What's your instinct? The resentment could be because he's trying to justify his actions, or perhaps he sees you as blocking the way to what he wants. I could be wrong, but it seems strange its happened after a trip out of town.
As for drinking, time will tell. It's possible he is sober but now obsessing about something else.
Look after yourself, keep your own mental welfare in the front of your mind and seek support. You can get through this, and probably to a brighter future.