I am having issues with a relatively new weed in my lawn.  It grows rapidly, spreads across the lawn, and crowds out my St. Augustine.  Much worse than last year.  Could not find it on multiple websites.  Finally found a potential match in Prostrate Knotweed.  Hoping to confirm or find out what it really is and how to treat/eradicate it.  Bad enough that I have had to pull buckets full of Virginia Buttonweed out of my yard to let the St. Augustine 'breathe', but now this stuff.  Covers at least a couple of hundred square feet of my lawn.  Will try to attach a somewhat close up photo I took with my phone.  Very think stems, elongated leaves.  Pulls up really easily but breaks the stems doing so.  Most of it is below my 2" setting on my mower as well.

Any help is appreciated.