You could try lightly killing the edge on your finger nail in the hopes of bringing both sides together at the same time. It is more common for me to have an area of the blade, like heel or toe, not undercutting, than one side. In any event, if you are not getting an even undercut your bevel is not set, which means it is not formed into a perfect 'V', likely more like a lopsided 'U'. I find a 30x loupe to be my best determining method for deciding when I need to move up or how I need to adjust my honing. Also, how is the hone wear? Are you using tape?