I live in Illinois and have a young son. His mother and I live together and have for the last 6 years. We have not been getting along and she keeps getting mad and saying I'm leaving for a while and then taking my child away for the weekend, supposedly to her mother's 2 hours away. (there is some question as to whether that is where she really goes). She recently informed me that only she has the right to take the child away for weekends or wherever she wants and legally I can't even take him 4 hours away to see my folks for the weekend unless she says so. Is this true. I really can't do the same thing she does to me and just say we're gong to visit my folks for a couple days. That would be considered illegal under Illinois law? My name is on the birth certificate and the child has my last name. I am tired of her threatening to take him somewhere every time she gets mad and just disappearing for days at a time. Right now, I have not heard from her for over 24 hours and don't really know where my child is.

She can go away with the child, and so can you. She has no exclusive rights just because she's the mother. All this has to be worked out in Family Court to make some sort of custody arrangements official, and who can leave when will be defined. I'd suggest that you file ASAP and not tell her right away, especially since you aren't sure where she goes. You don't have to have a lawyer but one would help.

You are both on birth certificate, you and her have equal rights, you can take the child or she can take the child, being or not being married does not make any difference.

What did she tell you before she left? If she gave you a time limit and has gone past that limit then file a missing persons report.
Since you are on the birth certificate you are the legal father and as of right now until a court says different you have equal rights to the child. Do not use the child for a pawn. That is the worst thing you can do. You need to stay on top of your changing situation and be proactive but be very careful about crossing lines and with what you say from here forward as it may be used against you.

Court action is NOT needed to establish that you are the legal father and that you have equal rights. You do not have to ask her permission to take your son to visit relatives. Just as she doesn't need your permission.

But if the co habitation is not going well, then you may need to file for court ordered custody and visitation.