I would not ask "are you txting?" only to say after her response "well, I know for a fact you are". Then why would you ask?

If you know then maybe just state that you will not pay for her txting other men as it is disrespectful to you. What she does for her own money is her own choice.

I struggle with communication as well, so I'm not telling you what to do, just offering my thoughts.

Together for 8,5 years.
S2
Interest in OM.
She left 29.09.12 b/c we couldn't work things out.
No signs of OM, not digging.
Living in seperate homes, sharing custody.