I used a tens machine off and on for many years - sometimes it would help quite a bit and other times, nothing.
However, about a month ago, I purchased an LED hand held light device to use for fibromyalgia pain. It is unbelievable. It emits white light that has had the UV radiation and heat filtered out. You basically hold it up against your aching muscles (for me, myofascial trigger points) and after about 10 minutes the results are amazing. The tight muscles literally melt under your fingers. The increase in blood flow, endorphins and ATP in the muscle creates some sort of event that forces the muscle into relaxation and the pain relief is astounding. I have had FM for 22+ years and this device is truly a miracle for me. My husband, who does not have FM, eliminated his daily headaches after one treatment to the muscles on the back of his neck. I would recommend this over the TENS machine.