Can you be just friends with someone you slept with?

In general, I would say yes, its totally possible to be platonic friends with a guy youve slept with.

Can text messages prove adultery?

Texts that you once thought were private can now be used, and many courts are starting to subpoena text messages to see what is inside of them. Yes, text messaging is now part of the modern world, but it can easily be used against you to prove that you were committing adultery, or that you have anger issues.