Relationship on Hold

Okay backstory.

My partner (guy) uses the Wickr app. On it he messages people and helps them out. A lot of the time he gets girls messaging him.

When he first got it we got into a fight because here was a girl he was clearly flirting with.

There was another girl he was messaging which he swore black and blue he wasn't flirting with (I believed it) but I came to find out not long after he WAS flirting with her. They would talk about my kids (which I look after as basically a sole parent) he would even send her pictures of them. When I found out we got into a really big fight over it to the point I wasn't sure if I even wanted the relationship to continue. But he apologised, blocked her and hasn't spoken to her since.

I've just come to find out it's happening again.. with a different woman this time.. yes I was going through his phone but hats because I get onto his account so that I can check if there are any new messages.. I was scrolling through the messages and realised who I originally thought was a male wasn't and that he talks to her quite frequently as if he was single..

Now, because of this I don't know how to come out to him that I know.

I class flirting as cheating (not sure if anyone else does) so I feel very upset and disappointed/disrespected.

I want to put my relationship on hold but I'm worried if I do he'll find someone else in our time apart...

I'm honestly so distraught (I'm literally shaking as I right this)

Is there a way I can put it on hold until he figures out what he wants without either of us going to other people....?