Workout Injury

I was doing my day-2 program this morning which included standing military press, pullup, deadlifts and squats. I finished the press and pullup and I was doing the deadlifts with 90 kilograms of weight when suddenly I felt a sudden pain on my lumbosacral area. This prompted me to stop right away. I told the trainer and he gave me a stretch which did not relieve the pain so I decided to just take a shower and go home. Of course this is not slipped disc, herniated nucleus pulposus nor lumbar sciatica. I therefore diagnose myself of having lumbar strain, hehehe!