@Blowingahoolly, I posted yesterday and apologize for assuming that your OH is male.
In my marriage, I would consider my H being on dating sites as infidelity. Like I previously stated, I would not do the pick me dance in any way, shape or form. If my H is happy to trash my trust and our family by hunting for illicit sexual adventures or emotional boosts, then he can return to singledom.
Your Wife is responsible for protecting her fidelity. If she had any issues with the marriage or in her life, she had a range of ethical options to use to deal with them. Instead she is making unethical, destructive choices by investing elsewhere/advertising herself on dating sites.
You may want to investigate further by checking her phone. When you confront, be ready for her to shed crocodile tears, lie, gaslight, downplay, or blame shift. Don’t buy into any of that manipulation.
As you don’t know how far she’s gone with this, you should book an STD test.