how it might be indicative of greater sins I would reassure you and say that the opposite is probably true
Based on nothing more scientific than having lived in Bangkok and Milan (both places where there is a certain tolerance for male business entertainment "proclivities") I'd say at best guess the odds are 50\50.
Incremental confessions have been a notable feature when working with men or their trailing spouses who have found themselves having to deal with an issue almost identical to that of the OP.
I'm not sure why that would surprise anybody. ICs are also a notable feature of spontaneous confessions of an affair, where the spouse is first informed it comprised of "just" flirting, a kiss, an emotional betrayal, just the once, the first time etc. only to discover at a later date that it was considerably more physical, more frequent and not exactly an irregular occurrence throughout their married life.
OP, I have no intention of telling you what you should do, think or feel, we all have our own unique blend of relationship history, circumstance and lines in the sand.
I do believe however that in a state of shock it right not occur to somebody who has not had prior experience of this sort of thing that face value cannot always be trusted as being the whole picture. Whatever you decide to do I think you are owed the opportunity to make those choices or resolutions from a position of being informed of the full extent of the breech of trust. It may have been exactly as he relayed it, it may not. Whether you choose to dig deeper or feel you can take his at his word is your call. You know him and what he is capable of doing. I don't.
I wish you both no more bombshells and a swift return to feeling on solid ground again. If you need any support in that process that you can't get in RL then the relationships board is a really good place to check out. These things are not always dealt with at light speed and you may find you have an emotional "hangover" from it for a while. Don't feel you have to struggle with that alone if talking it out and being listened to would help.
Big fat hug love, I'm so sorry this got dropped on you.