If he does not trust you now after 31 years and he is still your boyfriend you might be better with the Brother.
STEVE WILKOS! No, but if this is all of a sudden, that's usually what the person cheating does to try and take the focus off of them. This way you're not actually noticing that he's not around as much as he was or he starts a fight about it-then he has a "reason" to leave. ****, make him get a polygraph too! After 3 1/2 years, has his behaviors started changing? Just watch for it....he'll most likely pick a fight about it again
I would find it very suspicious that he is so vehemently accusing you of cheating.
Some screwballs out there will actually accuse the other of cheating when they them selves are the guilty party.
I have a friend who was in a similar situation. In the end she did go and have the affair that she was being accused of having and then told (hubby as it happens) that she wanted a divorce. Please do not put up with abuse and waste your life. It is too short. Lol
CHEAT on him with his SISTER. LOL