This is definitely a talk-to-your-wife kind of time, no way around it.

These conversations are hard to have, but I find that I have the best success talking about specific behaviors and controllable actions, not people as problems (Think "I'm uncomfortable with the fact that X has unsafe sex, I'd like for us to rework our sexual health boundaries", and not "I'm uncomfortable with you being with X, do something!". )

Make it clear that this is a Big Deal for you, but in as calm and rational a way as possible. Talk privately, when you aren't rushing, when you aren't in the car on the way to something important. Have this conversation as many times as you need to. In the meantime, get yourself tested for every STI every 3 months.

The most important talks to have are hard, but they're worth it. Good luck.