I'm going to make a recommendation for a book I've just started but so far am finding extremely helpful... Sex Addiction: The Partner's Perspective. I have tried other books but so far this is the one that is resonating with me the most. The reason why I recommend it to you is there is a section on misconceptions about sex addiction, and your last statement made me think of it. Basically, if your husband is a sex addict, he has been one long before you ever knew him, and therefore you have always been with an addict. It's hard to hear but what I mean is, he has ALWAYS been the person you thought he was. Many sex addicts are great partners, husbands, and fathers... and also sex addicts.
https://www.amazon.ca/Sex-Addiction-Perspective-Comprehensive-Understanding/dp/1138776521
That's a link to an excellent book for partners of sex addicts. There is also a book written by the same author for the sex addict.
Other comments provide great information, but just wanted to leave this piece here.