Hello, Anonymous.
Check to see if there are rules in your jurisdiction about what can and cannot be done in mediation. That will be your first guide as to how you may go about handling the mediation process.
As a general rule, however, you may bring up facts that support your argument. If the details you expressed above are true, and they lead you to feel one way about the situation, you should be able to tell the mediator as a means of explaining yourself.
However, bringing up embarrassing or hurtful details for the sake of destroying someone's character really won't help you in the long run as it will only make you look bad.
Since your ex-husband has an attorney, you may seriously want to look to hire an attorney to represent you. An attorney versus a non-attorney rarely ends well for the non-attorney.
I hope this helps.
Answered on Aug 18th, 2015 at 3:33 PM