Further to my ex won't let me see my children?

I just want to add some to what I said before as it seems people think I've done something wrong. My ex husband had my children for the weekend and wouldn't bring them back. We waited 4 months for mediation and then he asked for a DNA test which was never carried out it just prolonged going to court. We finally went to court and the judge said that because my children were settled in school and seemed happy they did not see any reason to unsettle them, I hope that explains things more clearly.