Tens machines are excellent, but can be awkward if you need to relive backache, as it'd probably mean lying on your tummy.
Please don't worry too much if you need an epidural. I had them, but they didn't take effect, so they were removed. I never felt the needle go in though, and half an hour after arriving back on the hospital ward, I went numb in an area about the size of a 10p piece! If it'd worked properly, I wouldnt've felt any pain at all. In fact, I truly would rather have a baby than visit the dentist - if everything's straight-forward, you don't have to get too upset about the labour and birth. Best of luck.