Hi, I'd like to help you with your question.
It sounds like there could be two things going on with your husband. One, his jealousy is about his own issues or two, he has a physical problem such as dementia.
When someone is jealous, it is because of several reasons:
One, they feel insecure. This is caused when someone feels they are inferior to others and are in competition.
Two, they are fearful of loss and rejection. They do not want to end up alone or rejected.
Three, poor self image. They feel they don't measure up to others and that other people are better than they are.
Four, low self confidence can cause a person to feel they are not good enough for you or the relationship.
If your husband suffers from any of these problems, he will be sensitive to what you do and who you see. He may even think of things from the past that make him feel jealous. If you feel this is the case, counseling can help you both overcome this issue.
But going back 30 years is a long time. If you have not given him any reason to believe that you have done anything in your marriage to cheat or otherwise, then his reasons for bringing up this issue now cannot be easily explained. That is what makes me think that his problem might be physical in origin, especially since he now brings the topic up everyday.
As people age, they can develop a dementia. Jealousy can be a symptom of dementia and become unreasonable in it's intensity. Dementia can start at any age but is most common in later years. You may want to ask your husband if he would be willing to see his doctor for a check up. Before he goes, call the doctor and let him/her know what you are noticing. That way, they can screen your husband especially for dementia.
I hope this has helped you,