How do you avoid being goofy when you want to be sexy? Regardless of your roll in a power exchange relationship, sexting can aid you in establishing and maintaining a feeling of power or powerlessness.
If I had only occasionally checked his phone calls or texts, the behavior would have been brought to light much sooner.
Then you both should be able to figure out what the real problem is.
For me such texts would cross a line, too.
It went to his mom.
Relationships require some balancing between individuals owning their insecurities and not using them to control their partner and being respectful and accommodating of their partners comfort levels.