Past Years Roth IRA Excess Contributions (MFS)

I married my wife in 2014 and realized I have been making excess contributions to my Roth IRA (I put the maximum in every year).  We filed MFS in 2014, 2015, 2016, 2017, and 2019, but I was only able to contribute to Roth IRA if MFJ.  Am I able to amend my tax returns to MFJ going back to 2014?  Will this avoid the 6% per year penalty for excess contributions?  The IRS has never contacted me about the excess contributions.  Do I also need to fill out form 5329 for excess contributions if I amend my tax returns?  

 

@dmertz