I agree that you should contact a family law attorney. Though you could attempt to bring a claim against him for intentional infliction of emotional distress, you would need to show that you've suffered severe emotional distress and that his conduct is so egregious that it should not be tolerated in a civilized society. While it sounds like he is harassing you and he's most definitely causing you distress, it is a hard to standard to meet. I suggest you talk to a family law attorney and look into a restraining order.
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Sounds like your ex is a jerk. Unfortunately, he is a jerk with whom you have a child, and as you have discovered, being a jerk is not a crime. Baseless motions should be dealt with by your family lawyer, who can pursue sanctions in family court. Filing a separate lawsuit is just going to give this jerk another forum in which to subject you to his offensive personality. The time and money involved would be better spent getting you and your child some professional assistance in dealing with the emotional stress. Good luck.
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Use the AVVO 'Find a Lawyer' tool bar and select a family law attorney or two and get a free consultation and ask questions and allow the attorney's to also ask question so that hopefully one of them can assist you.