Can my ex-girlfriend keep me from seeing my son whom i have alway's supported

I have alway's worked and put every penny into our expenses, my ex, her daughter, my son and myself. she worked about two month's in the begining of our relationship. we split up and i moved home but continued to pay her rent. she started going to the bar's and I had both kid's 85% of the time. she would drop my son off for ten days at a time pick him up and return him 2 day's later. i lived with my mom who was just glad she left him with us and would watch him while i worked. this went on for about 8 months then one day she up and moved to another town with some guy and cut me off completely. i have no idea where my son is living or whom he is living with. i have alway's paid her child support. she has filed papers with the court giving me everyother weekend and she is asking for child support from the day my son was born. I don't know what to do but most of all i miss my son and i am very worried about him. he alway's cried when he had to leave with his mom. Can she keep him from me is my question. i haven't seen him for two month's and my whole family is just sick about it.

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