Evening Primrose Oil-Help/Advice

This is our 6 month of trying.  I'm 37 years old and have been using OPKs and last month started using PreSeed but read about EPO.  One site I read said to use it only on days 1-14 of your cycle.  Anyone have any advice or has had any success in using this?  I think I could benefit from it since my CM doesn't seem to be what it used to be.  Also, does increased water help CM?  Thanks for your help!  Baby dust to all!