Lower back spasm after kettlebell swings

Hi all,

As the title suggests, I was doing 6kg kettlebell swings yesterday at the gym (nothing new here - I normally do kettlebell swings at around 12kg) when I felt something "tug" in my lower back. It was slightly painful but the pain went away pretty quickly, so thinking nothing of it, I finished off my session and jogged home.

I had a pretty poor night's sleep and woke up this morning in excruciating pain. I've had severe back spasms all morning, that have been so crippling I've sometimes collapsed and have been unable to stand or sit. I've been lying down for the last few hours but the pain is getting worse if anything. I can't lie on my side and any sort of movement is extremely painful.

Any ideas? Many thanks in advanced :)

Hayley