I am divorced for 3 years now but started my job 5years ago and have not updated my status on my w2 to single. What do I do?

That's ok.  What you claim at work doesn't have to match your tax return.  That's only to tell your employer how much withholding to take out.  I'm married but claim Single at work to have more taken out.  But you should give your employer a new W4 to update it.  

It sounds like you're trying to explain your withholdings are for two or more people. If that is the case, less money is being withheld by your employer. You can always go to your HR office and change your status by filing a new withholding amount. 

The W-4 you give to your employer does not dictate how you file your tax return.  It just tells the employer how much tax to withhold.   You can change your W-4.

https://www.irs.gov/individuals/tax-withholding-estimator

https://www.irs.gov/pub/irs-pdf/fw4.pdf