Your employer may be violating the Fair Labor Standards Act. That depends on whether you are exempt or non-exempt from the Act.
Check the Texas Workforce Commission's web site. The Workforce Commission has information on the Fair Labor Standards Act, what employees are exempt and which are not, and when an employer has to pay overtime. There are some new cases where if an employer requires an employee to be on call over the weekend, and that weekend time results in an excess of 40 hours, the employer could owe for overtime pay.
If you are an hourly employee, you should be paid time and a half for any time you work over 40 hours in a one week period. Some salaried executive and administrative workers and professional workers and some commission workers are exempt from federal overtime laws. You shold consult an attorney who is experienced in wage and hour law for additional counsel.