In addition to it being a reflection of his character and attitude towards yourself & the relationship, op .... It is possible his stone walling of you was time buying ...
He was caught on the back foot, he wasn't prepared, he didn't have a story ready, or many excuses, he also needed time to go through all his communications (and possibly even accounts) and check what you might be able to find. He needed to know where he stood in terms of exposure etc.
(He may also have been checking out legal and financial things, since he's bound to realise many a woman would end a relationship over this, sooner or later).
As another poster commented, it seems unusual to get caught the very first time (or 3 times in one in one incident to be accurate) you do something..... So it's not beyond credibility that he was stone walling you to check everything that could be found and trip him up and get rid of it.
He needed time and space to father a defence and a strategy, he may also have been covering his tracks.