Legal Question in Criminal Law in California

Too late. You entered your plea, voluntarily, and confirmed that on the record at your sentencing. You don't get a 'do over' in criminal court after being sentenced, nor get to claim 'duress'. Every defendant is under 'duress' and pressure to avoid jail while plea bargaining. Fact of life. Accept that reality, and the consequences of your decisions and conduct, and now move forward in life.

Everyone who accepts a plea deal is under pressure to do so. After all, if they don't they risk a worse outcome at trial. Deciding later than you should have rejected the deal is not sufficient reason for the court to let you out of it.

There are grounds on which defendants can be allowed to withdraw their pleas, but these grounds do not come up very often. I have no way to know whether any are present in your case.

You should discuss your situation with your lawyer ASAP. I hope you weren't foolish enough to make a plea deal without a lawyer, but if you were and you want to get out of the deal, then you should get one right away.