Unplug the sensor from the wiring harness, and get a special O2 sensor socket from the auto parts store (some loan them out for free) and remove the old sensor from the exhaust bung. If the sensor won't budge, try more penetrating oil or attempt the removal with the engine warm (be careful not to burn yourself).
However, a mattress that is too soft is just as bad for low back pain as a mattress that is too firm. In a 2005 study, The Journal of the Canadian Chiropractic Association pointed out that in a survey, 76% of orthopedic surgeons recommended firm mattresses.
The typical back sleeping position places strain on the lower back and neck. Normally, the buttocks and the upper back are in contact with the sleep surface, while the lower back is minimally supported. This posture can strain the lower back and cause pain and discomfort. Traditional pillows often provide minimal neck support and induce neck strain in this position.