If your employer employs 5 or more employees, and if you can prove that you were terminated because of your disability and not the many other reasons they have stated, then yes, you might have a claim for disability discrimination. The difficulty may be proving that the reasons given for your termination were not truthful and that the only reason you were terminated was your disabling condition. Assumptions will not be enough.
If you think that is possible to prove the pretextual nature of the employer's reasons for firing you, you should contact an employment attorney and discuss the situation with him or her and get some solid advice about your situation.
Good luck to you.
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Following from Mr. Pedersen's great response: one way to help prove discrimination is by showing an adverse action that followed close in time to the employer's first knowledge of a protected status. However, in your case, it will be hard to show this because your overall employment was short. But "hard to show this" is not the same as "imposible," so you may have options.
A clearer path to some sort of recovery is that you were being paid under the table. You and your former employer both know this is illegal, but your former employer has a large economic incentive to hide your employment. You will have to report and pay taxes on your wages, but your former employer has, potentially, committed tax fraud against the federal and state governments; insurance fraud against its workers' compensation carrier; failed to pay into Social Security, FUTA, unemployment, and other mandatory accounts; and more. Your employer may want to negotiate a resolution to your termination rather than risk you filing a wage claim with the Division of Labor Standards Enforcement and being found out.
For the under the table employment and the potential disability discrimination, you should speak with one or more experienced employment law attorneys with whom you can discuss the details of your situation. To find a plaintiffs employment attorney in California, please go to the web site of the California Employment Lawyers Association (CELA). CELA is the largest and most influential bar association in the state for attorneys who represent working people. The web site is www.cela.org. Click on "Find a CELA Member" and you can search by location and practice area. Many CELA attorneys represent clients throughout the state.
I hope you can resolve your situation and wish you the best.
twitter.com/MikaSpencer *** All legal actions have time limits, called statutes of limitation. If you miss the deadline for filing your claim, you will lose the opportunity to pursue your case. Please consult with an experienced employment attorney as soon as possible to better preserve your rights. *** Marilynn Mika Spencer provides information on Avvo as a service to the public, primarily when general information may be of assistance. Avvo is not an appropriate forum for an in-depth response or a detailed analysis. These comments are for information only and should not be considered legal advice. Legal advice must pertain to specific, detailed facts. No attorney-client relationship is created based on this information exchange. *** Marilynn Mika Spencer is licensed to practice law before all state and federal courts in California, and can appear before administrative agencies throughout the country. She is eligible to represent clients in other states on a pro hac vice basis. ***