Can access files but no longer write?

have had the WDBAAF0010HBK 1TB My Book Essential for going on two years now and havent had any problems until recently. 

i can still access all my files but i can no longer write to the drive. even something simple like trying to create a folder will yield this windows error message: “cannot read from the source file or disk.” but it obviously can read because i can still access all my files. 

any ideas? 

the only strange thing with the drive is that for some reason the drive stopped letting me eject it awhile back. even though no files were being used it would tell me files were in use, so i would have to wait until i shut my computer down to eject it. okay no big deal right? or so i thought until i noticed this i could no longer write to the drive. 

im sure a format would work but i dont want to lose all my files. i dont exactly have another hard drive sitting around which i could just dump these 600gbs on so its a bit frustrating. 

Something simple to try first. Go into the device manager and delete the driver for the drive. Remove it and reboot system and plug back in and it will load a fresh driver. Are you using any backup or sync software? I use GoodSync and then the drive won’t eject unless I log off and back on.