Porsha Williams' Boyfriend -- I'm Returning My Porsha

The 'Real Housewives' shows have a big problem ... they build their seasons around romances that blow up before the shows air.

Porsha Williams is the latest R.H. star who happily filmed burgeoning love that flamed out. She hooked up with Buffalo Bills star Duke Williams and they cavorted for season 6 shows, but when the cameras stopped rolling they stopped too, only after a few months of dating.

The problem ... viewers know the relationship is history, so the storyline doesn't ring true.

Porsha doesn't have a problem scoring a touchdown on the playing field ... she just can't hold out for the win.

It also happened on "Real Housewives of Beverly Hills," when Brandi Glanville dated a real estate agent but they were dunzo before the shows aired.