Missed birthday and now she is taking me to court

My son is now three years old. things just didn't work between his mother and i. i spend as much time with him as i can but i recently moved up north and have been laid off during the winter....she says when i have a job i work too much to see him and when i dont have one i cant support him to see him. Then when she brings him around she stays because she thinks i dont pay attention (which i do) thus confirming in her mind an image of an unfit parent. How can i be an effective one if i dont get time alone with him. yeah i live with my parents but they help make a stable environment. problem is i missed his birthday, and now she wants to get full custody and child support. i had a ride to go there for his birthday but the ride fell through. my car is broke down and my girlfriend had to work so we werent able to make it. we suggested for his mother to bring him up for a birthday party up here with his family here, but she refuses. i really dont get to see him becasue of her and it kills me inside. i try to be a good dad given the circumstances. i dont know what to do.