How long can a person claim statutory rape after the sexual encounter?

First I need to say that I am sorry for your situation and I hope that you get the help that you need with all of this on an emotional level. 

Florida has a statute of limitations for sexual assault in both the civil side and the criminal side.  I am going to focus on the criminal side.  Here is what I have found:

For criminal cases, a prosecutor may file a charge of aggravated rape at any time, regardless of the age of the victim and with no time limitation (an aggravated rape is generally a rape that involves a weapon, more than one person, or seriously injures the victim).  

Prosecution for sexual assault or abuse has a statute of limitations of four years.   However, there is an exception made for DNA analysis, which allows for the prosecution of a rapist anytime within one year of the discovery of DNA evidence, even if it is discovered after the ordinary statute of limitations period ran out.
 
In regards to child molestation specifically, there have recently been many changes to the statute of limitations nationwide.  Indeed, eleven states have completely removed the limitations for child-sex crimes in the past 10 years.  But after the Supreme court ruled that retroactively changing the statute of limitations (in order to prosecute crimes from long ago) was unconstitutional, many states were forced to scrap plans to do just that (Florida was one such state).  The current law only allows four years from the date of the incident, but the law is likely to have changed as of 2006, where there was a push to extend it to 10 years.  

What's more, Florida has an extremely large number of complicated exceptions to it's limitation rules, so you should talk to an attorney familiar with Florida law for the most up to date information.  Good luck to you.