The simplest explanation is likely the right one. Either prostitutes or an affair.
If he's emptying his balls into the bought bodies of prostituted women, he may not see it as infidelity, but it speaks everything about him.
If it's an affair, his heart and mind is also elsewhere.
Decide what you want out of the rest of your life.
Photograph the evidence in situ in his drawer with his socks, in case he bins it.
See a solicitor and find out your rights.
Get clear on your financial situation.
Then speak to him. As others have said, there will be a tick list of excuses flung out. The poshwank, holding for someone else, intended for the conversation with the teen later on, someone put them there as a joke, they're old (explain the expiry date, then?) bla bla bla ...
Then say what is going to happen.
It's going to be hard but letting this trudge on will ultimately be harder.