Have you previously thought that your significant other may be hiding something from you. So I didn't think and got burned in my life. My ex-boyfriend cheated on me, and I didn't even think about it. I thought for a long time how to get into his phone because there was a password there, but once I succeeded. I installed one application, it is invisible. Here
https://www.laocentermn.org/how-to-log-into-someones-facebook-messenger/ you can read how to install this application and read messages. I think it will be interesting for you. After all, it will never be superfluous to check your partner, especially after my Bitter experience ...