Hi paul,
i'm probably the one whose posting you read that suggested not opening the mouth wide. The jaw is a very complex joint, or two if you want to get technical, but in a way, one as they must work together. You have been playing with fire a little bit by moving your jaws side to side. There is a good possibility that either one of your discs slipped or your muscles rebelled.
First - see your dentist. Not all dentists are familiar enough with tmj to treat it but you might just have some overworked jaw muscles and he should evaluate you. Doctors' usually start with a two-week prescription of valium for night time. Treat your jaw like it's been severely sprained. Be very gentle with your jaw. Try and get some good nights' sleep, try not to pop your jaw, watch your posture in front on the computer and do eveything you can to relax your muscles in your shoulders, neck and jaw areas.
The problem with opening the mouth wide is that it can cause the disc(s) to get caught out of place and that then stretches the ligaments and tendons, etc. Exercise is good, but I think it would be best if your family doctor can refer you to physical therapy with a therapist trained in tmj problems. Check out the tmj physical therapy page at nismat.Org.
It's good that you are researching over the internet and going to support sites. Education is your best defense, but also be very careful. Always play it safe. Nothing drastic or irreversible and I can't stress enough about posture and . . . Stress.
My belief is that you are at the very early stages of tmj and I firmly believe that tmj is "curable," so don't be discouraged. Take care of yourself and if there are any other questions you might, please feel free to ask. Or, just stop by to talk tmj if you want.
God bless...
Carol