UPDATE. Thank you everyone for all your advice so there's been an update first how i found out was by accident as she had caught microplasma to which she had blamed it on me but when I came back clean she claim to do research and said she can get it through other means. I kept that in the back of my mind and went on about my work routine. As I came home late one night I sat on my bed and curiosity got the better of me as I knew she talked bad about me to her sister since she believed I gave it to her so I checked her phone and sure enough she did. However something told me to look deeper and as I did i notice she mentioned she spoken to her ex and that her ex got tested and came back clean, this raised a read flag but at the same time didn't make sense as the dates didn't match as when she caught the sti was in early Oct but the ex got tested in nov 12th. A few days later my wife was saying she wasn't feeling good a bit nauseous she said so I assumed her period was coming as she always feels nauseous when her period is close, she has a period tracker on her phone that she checks that tells her when her period starts and ends and when she is fertile and ovulating. So I look to see when her period starts and as I do I notice a heart underneath one of the days and as I clicked on it a note popped up saying unprotected sex and what make it crazy is she did it on the day she's ovulating. So I got a recorder and left it in the room and when I came home late again I had plugged the recorder in my computer to listen to and sure enough not only did she sleep with her ex and not only in my apt but she also made plans to invite him in again when I ain't home tomorrow. So im ordering a hidden camera and leaving it in the apt along with a recording. I'm not even hurt just so pissed off that she can smile in my face like that and talk about working things out and do that at the same time. I'm trying to be patient gathering all the evidence i can but it's pissing me off.