What to do when betrayed spouse can't believe story

Haven't been in that situation but, since your spouse already knows you're capable of lying, he or she is likely to no longer believe a word you say.

Your spouse must be hurting greatly. Lies upon lies.

Stop trying to convince him of this "ridiculous" event and concentrate on being a good spouse/partner.

Time reveals all, including the building up of trust. Unfortunately, it takes time for that to happen.

You sound desperate for trust to be granted ASAP, when YOU want it.

Thanks for your responses -
I'm in no hurry for my spouse to trust me - I know she can't...
I'm not trying to convince her of anything either - she is questioning me - I answer her questions - but she is unable to believe the story because it doesn't quite make sense... it's not a typical affair type story - even I know how ridiculous the story sounds - however, I am providing her the truth of the story - she is unable to believe what took place.
I'm not desperate for anything to do with me at all.... I am desperate for her to start trying to heal - yes - so when I answer her questions - I'm trying to help her by giving her what she needs - but the truth is inconceivable to her... that's all I'm trying to say...

Have you asked her what would make her/help her believe what you are telling her?

Perhaps the issue isn't the odd circumstances, but the favourable to you slant you put on it when telling it?