I think it's good you are in therapy.

Have you explored why you feel threatened by other women? I think the underlying insecurity is the issue here. He chose you, you were his choice, but it's not reasonable to expect him to not contact colleagues or friends in an appropriate context.

I agree with Bill that it may be unhelpful to keep checking his phone, in fact it might be feeding an anxiety you have - and as you have found out it is not a sure fire way to track his communications. There is no sure fire way to track communications - that is why couples ultimately have to trust each other.