If I understand your story, all of the sexual indiscretions you committed were before you married---over 19 years ago. Is this correct? You lied about some of this stuff during marital counseling sessions after you were married, is this correct? So it is the basis of your lying that informs him that he cannot trust you anymore, I trust?
If the above points are all "correct", your husband really has just two reasonable choices to make, and you can help present the choices to him. His first choice is simply ACT on his belief that he cannot trust you (and conclude that he probably never will;); and therefore, it really makes no sense to stay married to you. he should divorce you if he truly, deeply believes this. Alternatively, he can choose to stay with you, but ONLY if the two of your lay out a path toward forgiveness and letting the past stay in the past. This means being willing to put the past behind the two of you and never talk about it again---not ever; not during any arguments or future problems. It means reflecting on the past 19 years and assessing whether your behavior has been consistent with that of a faithful wife (not the lying that occurred during your marital counseling), but your ACTIONS and behavior. You've never cheated on the man following the marriage, is this not correct? So he bears the burden and responsibility of deciding whether he wants some peace and relief from his concerns about your trustworthiness, and act 'as if' you are starting over and trying to build trust with one another, much as a newly married couple might. People make mistakes. I suspect he has made plenty of his own, which, if someone had not stepped up and forgiven him for, he would yet be suffering today.
Either of these alternatives are worth considering, but the second alternative is much more rational. He may have not married the sexually inactive woman he thought he did and prior to your marriage, you may have acted up during your courtship. I suspect he has no basis for suspicion and no evidence, because there is none. The current circumstance however, with your marriage is completely untenable and 'unlivable' going forward. That is, it makes no sense whatsoever to stay in a marriage in which you are forever holding lies about premarital infidelity over your spouses head day after day, when these things actually occurred prior to your marriage, and over 19 years ago. And, yes, he may have been upset about the lying about your past premarital relationships. But frankly, if he cannot believe that and won't "let it go and move on", then once again, he may be impossible to live with in a relationship, going forward. You really have no marriage. So the burden is really on him to make a decision. If you make a decision to try to put the past behind you, I would absolutely find a good clinical psychologist who does marital therapy to help you out. The last therapist you had acted irresponsibly in allowing a discussion of your premarital past to enter into ANY discussions of any topic you were facing. No interrogations during the therapy should have occurred, such that, you were put in a position of having to decide to lie or not. Anyway, if he decides that he wants to stay married to you, it can ONLY be under the condition that you return to marital therapy with the sole purpose of figuring out what each of you need to be doing today and tomorrow and the next day, to build trust in one another. No discussion of the past, period.
What do you think?