talk to your embassy, make sure you have plenty of copies of the contract and make sure there's no small print or loophole your employer is using. Maybe talk to your sponsor also. You can try to file a complaint with the Qatar Ministry of Labour, but I'm doubtful you'll get a response or at least not one you like. Really anything labour related is an uphill battle in this country. It's much easier for an employer here to terminate an employee and find a replacement than to listen to their complaints.