How would I go about getting legal aid in Texas

It is possible that the Office of the Attorney General shows that you owe a large amount of money to your child's father.  I recommend getting a copy of the financial transaction record for your case from the Office of Attorney General's office or website.  After that you may want to enlist the help of the child's father if he will agree that you do not owe him support.  There is something called an affidavit of direct payment that, if true, the OAG may accept and wipe out some or all of the child support arrearage.  If you and the father have been living together the full time then you may be able to get a credit for that time.  There may be a court order somewhere that orders you to pay support and provide health insurance or pay medical support.  Finding out what is ordered is the starting place.  Then you need to try to get the orders modified if they order you to pay support.  You do not need legal aid to help you with this. You should be able to handle this yourself.  Legal aid probably would not take on a case to help you eliminate an obligation to pay child support.  That is not part of their mission.