if i am 25 and my ex is 17 and her parents are threatening to go to the da about our relationship and we have been broken up for like four months now is there a time limit to when they can bring charges saying we had sex and if i denay it is it my word veres hers how should i handle it

The statute of limitations to bring prosecution against a person depends on whether the charge is for a misdemeanor or a felony violation. In your situation given the age difference between you, if the DA decided to file charges it could be either one; a misdemeanor or a felony according to the statute 261.5.

Violation of Penal Code section 261.5(b) is a misdemeanor and has a one year statute of limitations.
Violation of Penal Code section 261.5(d) is a straight felony and has a three year statute of limitations. The statue of limitations runs from the date of the offense, regardless of when it is reported.

If charges are filed, it is in your best interest to seek representation from a criminal defense attorney who specializes in sexual offense cases. There are many to choose from and generally one to fit all budgets.