You need to mount a defense if you want to be a part of this child's life....or you could be ordered to pay for 18 years and have no chance of ever seeing the boy.
Guardian Ad Litems (GAL) can be very cool. Basically what has happened is that the mom has said your rights need to be terminated because you are a detriment to the child by either your presence or your total absence. Now every time a parent files on of these the state appoints a Guardian Ad Litem. this person is usually a lawyer, but not always in every state. This person will go and investigate and see if the child really would be better off without you in their life. It is usually difficult to terminate a parents rights, but it can be done, but it requires you to be VERY neglectful to the child or for you to have actually harmed him or another child in your care.
In my state of GA there are about 10 criteria and my step son's bio mom falls into several! We plan on going to terminate her rights soon, in her case she has gone over 12 months without paying her child support, she has made no attempt to see the child in the last 6 months, and other things like that.
If you visit with your child, or try to visit with your child and the mom has blocked it you need to tell the GAL. it does not matter if the mom has remaried and she wants the step dad to adopt the boy, the fact is you are the dad and you have rights, she can't just choose another father, but with the title of father comes rights and responisbilities and in order to get those rights you have to be living up to those responsibilities such as visitation and child support.
Sometimes mothers just file to get you out of their lives because only THEY know what is best for the child, and that is why the state always appoints a GAL to really see what is going on.
A lot of counties have a website and a judicial records search. You are able to search criminal or civil records. Check out that counties web site and see. Otherwise you can probably go to the courthouse and get the information.