How do i owe 20,000 worth of child support!!!!!??

I married my wife in 2002. A child support order from the state of texas had been filed when she and I were in college and had our son (she went to go get WIC or TANF or something and they automatically put me on child support) my son was born in 1998. so during this time in school the state was sending her a check , i suppose for the child support amount or just state support or something which when i got a job i had to pay the money back that the state gave her. That money came out of my tax returns which was fine. Then we got married after i went into the army. that child support order came back up and the army was paying it for me as part of my pay or something to that effect. the problem was that it came out of my check but the money came back to the same household 2 or 3 weeks later which started making me late on bills and whatnot.....so she wrote a letter to whoever to stop the child support and give me credit for all amounts owed or something like that. so all the support stopped. then when we separated after i came back from iraq all of a sudden i get a letter saying i am in arrears for 20,000 and they suspended my drivers licences and all kind of crap. i called to the support folks and they said as long as a support order is on the books they don't have to necessarily collect on it but the money accrues still even if all the charges had been dismissed from my wifes letter ( which by the way no one seems to have any knowledge of the letter or all the stuff we did to get the support stopped anyway) so i say ok why did the collection effort stop then and they have no answer except pay the money,....im like how do I owe for all the time since my son was born when i basically have been taking care of them the whole time.....they say pay the money....is this correct?????? Has anyone else had this situation??? what did you do to resolve it??? was a lawyer necessary??? I don't believe i owe this money. We were married, they lived with me, i was the sole income, medical and all that through the military, the letter she wrote erased all the prior charges (i thought), WTF.....I am unemployed now and was trying to get a job but my license suspended and when employers run checks they see that.....so i called to see how to get my license unsuspended they say pay the support......OK I HAVE NO JOB and i'm not sure but i probably have a warrant for arrest because of owing more than 2500 for support WTF,,,,what do I do