Hi
I had gone through the question and understand your concern
I have seen almost similar case in my clinic.
In my opinion , your husband is suffering frim "othello syndrome". In this condition person usually thinks that his/her is cheating .
The right thing to do is to gain his confidence by talking to him.about it and
consult a psychiatrist.
Consultung a psychiatrist would be of great help for both of you.
If tbe psychiatrist prescribe any medicines, then make sure that he takes it daily.
And yes , staying apart do increases the chances of such thoughts.
If i were the consulting doctor , i would have prescribed him.tablet arip-mt 10 to be taken at night after dinner .
Hope this information helps.
Let me know.if you have any other queries.
Thank you