There are three reasons for finding condoms in his bag.
He's using prostitutes. Meaningless (to him) way to deal with no sex at home.
Check the credit card and bank statements for odd payments or cash withdrawals.
He's having casual flings.
He's fallen in love and is having a secret relationship.
Decide what you think and feel about each one, bearing in mind they could be male or female.
Don't just ask him casually 'is there something I should know, are you having an affair?' etc. He will lie and gaslight you and attempt to make you feel you're imagining things.
Just check the bag, put it on the table, put the condoms in front of him and tell him 'you need to explain this now'. Watch his face and body language.
He will attempt to get out of it, generally using:
- I didn't know they were there
- Someone put it in my bag for a joke
- I'm looking after them for someone else
- Poshwank
He will also attempt to deflect:
'Why are you looking in my bag? Are you spying on me? How dare you?'
And this will, somehow, be twisted as your fault. 'If you hadn't (insert bullshit) I'd never have (insert more bullshit).'
Be prepared to discover, as so many women here have, that you never really knew him.