Just don't get in your feelings with her. It's your house(it IS your house, isn't it?). Do NOT move out. Just be cool. Be a good dad. Don't even be a diick to her(don't act butt hurt). Just don't trust her, and start covertly collecting evidence. Don't discuss anything with her. Everything is fine.
Now, realize your own part in this mess:
1) you entered your marriage with your eyes tightly closed, and then decided to ply then wide open...AFTER the wedding and birth of your children, which is completely bassackwards.
2) you role played being her previous lovers(and for all you know, current lovers), with her, which is just pathetic...and doesn't exactly earn her respect.
3) you suggested wife-swapping to your wife, making yourself look like an eager cuck.
I'm not stating any of this to dump on you. I'm just trying to point out that you made your own bed.
Just don't get emotional with her. Treat her like you would a valued employee, not irreplaceable, but valuable enough to not run off immediately.