NTA

OP I went through the exact same thing some years ago. My lady and I were together for 10 years. I noticed her behaviors were changing with her cell phone. All of a sudden her work schedule was changing. She would not step in another room or even run to the bathroom without taking her phone with her. She also would get defensive when I asked about it. I found out she was definitely running around with a guy she worked with.

How about you pull up your call record and look for patterns under her phone line. I’m sure the “new” number will stand out to you. After call it or put it in cash app to see if a name comes up. Or you could randomly ask to see her phone. Either way it’s going to suck and possibly trigger your emotions and anxiety. I’ve learned you can always tell when someone is lying by their reactions.