this is not all your fault. I'm sure you can provide more details as well, but don't blame yourself. 38 years of marriage is great. You obviously did something right and can provide us with great advice too.
Avoiding conflict is obviously not the best thing to do. It's how we address our differences that really matters. That doesn't justify him cheating. Worse even, there is very clearly an emotional affair (EA) and who knows if there has been more.
It sounds like he is looking for some 'Words of Affirmation' or 'Quality Time' with you when he is angry and venting. Michele has a scenario like this in Divorce Remedy, and the wife ended up listening, validating, and then jumping on the her husband's "side" of the argument, almost more passionately than her husband. That may be a good 180 for you.
You are not worthless. You are a human being with real thoughts and emotions. Your husband is not without blame too. What he did and is doing with the other woman (OM) is just plain wrong. All those times he was talking to her, he should have been talking to you.
Continue to read other threads and post in yours, more details would be great.
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.