I think I'm about to break off my engagement

I've been having a hunch lately and I'm pretty sure my fiance is cheating on me. I found an ad on Craigslist that sounds just like him so I've been emailing it. Now today I'm just following/stalking him and waiting for the right time to ambush him. I guess my plan is to follow him to the meeting spot, walk up to his truck and throw the ring back at him and tell him to find someone else to wear it. I just need to get this out there, to help calm my nerves. *I should add he's done some shady things in the past similar to this. I don't need to put in all the other details that go with it. **We're supposed to meet somewhere where not a lot of people go, especially when it's raining. I'll know if its him cause when I pull in I'll either see his truck or I won't. If it's not his truck, I'll just turn around and leave and the stranger never knows. *** The reason I say it sounds like him is cause a long time ago I found something almost the exact same in his email and he said it was just his old college buddy messing with him and I couldn't ever prove if he was doing something. Whenever I asked about it or tried to talk to him about it he just acts like I'm too stupid to figure it out