Sounds like a convenient excuse to me Ru!
I had a boyfriend some years ago who did exactly this. We'd been dating a few months and we'd had the exclusivity chat. It wasn't love but y'know .. It was ok!
I was on the site closing my account when I checked on his. It showed him as active within the past 24 hours. I thought ' hmmm' and left my account as it was and then spent a couple of days checking. It showed him at various times online.
I just called him and asked. He said he was on there trying to close his account. I said, ' what, for the last three days? ' and he said ' it's just difficult finding the right area of the site to do it '
I didn't believe him. So I just knocked it on the head.
I honestly think that online dating IS all about seeing multiple people and dating etc. why not? And I don't actually see a need to completely announce this it someone you're dating as such.
But if you've had a chat about not seeing other people then it's poor behaviour to keel having a little look ' just in case .. ' I mean, when do you stop doing that?
So I really would ask him directly and pleasantly with no apologies or explanations as to how you know. That's kind of irrelevant. Have an honest chat. And don't be fobbed off.
I'd probably ditch him and find someone else. Life is too short to be with someone you can't actually trust. The exception would be if you liked him enough to keep dating him but also saw other people yourself. Is this something you could do? If not, then get rid