I'm Having Am Issue With My Back That I Was

I'm having am issue with my back that I was pretty much brushed to the side earlier at urgent care, and I was just trying to get a question answered... I was lifting some heavy things on Saturday and hurt my back(low low-L4 or so) and it's gotten progressively worse... Usually if i take the pressure off the discs(exercise ball/inversion table) it feels much better, but this time around, as soon as the natural pressure is put back on the area it is immediate excruciating pain. Is this just a muscular strain, or does it sound more like a disc related injury? My Dr is booked solid until Nov 18th so I really want to figure this out sooner than later...