my ex girlfriend won't let me see or talk to my kids what should i do

Not nearly enough information was provided to permit any kind of meaningful response.  Are you on the birth certificates of these children?  Have a relationship with them?  Where is everyone living (both what State and what residence) and who moved where when? First, I suggest that you take a look at a couple of resources: http://willicklawgroup.com/child-custody-and-visitation/ http://willicklawgroup.com/paternity/ Then I suggest that you confer with a knowledgeable family law attorney, in this office or some other, to get answers to your specific questions based on your specific facts.