Need advice from ladies who have given birth with an epidural please!

So my midwife and I discussed my birth plan and when I told her I will likely want an epidural she said the most likely positron I'll be laboring in is on my back. This worries me because that's the last way I want to deliver. I was at least hoping she would say I could birth on my side? But she seems confident that my legs would be "too numb for other positions". How is this the case when I have heard of women getting epidurals and delivering while side lying, on all fours, etc?