I wouldn't investigate at all at this point. He's "unsure", so it's not like he's saying "I'm in this, let's figure it out". To me, there is a huge difference and you'd be setting yourself up for more hurt. I've also seen folks investigate before spouse really knows what they want and they use it as a tool for themselves to be "done". "See, he/she is still lying, cheating etc".
What's your real motivation? What would knowing mean to you?
