Ever pulled anything? Have you ever bent over too far, or bent backwards not quite enough. Why would you do such a thing? Do you think this has something to do with you doing similar things over and over? You might possibly have what they call a repetitive strain injury. A repetitive strain injury is an injury that results from straining a muscle repeatedly to the point of injury. I have personally experienced this and it is no walk in the park injury. I mean, you literally will not be able to walk in the park. A repetitive strain injury can go away on its own, but sometimes it will not, and it needs a little coaxing. So we go about our day to day and hope we don't encounter such things. If you do, first things first: don't panic. This can be one of the worst things you can do. It tenses the strained muscle more, making you have a worse time.
Second, you should immediately after calming down consider calling a health care professional that has experience dealing with repetitive strain injury. Preferably a physical therapist, they will be able to inform you of the many natural ways to relieve yourself from this strain. You should be ready to stretch and strengthen these muscles. That is the main cause of this injury in the first place. Your muscles are weak and for that reason you hurt yourself again. Stretch and go to the gym. It will do you a world of good. You will be fitter, happier, and most overjoyed.