I see this question was 5 yrs ago. I'll give you my experience on car anyone is afraid or anxious about it. I've had 2. The first occasion I did exactly as I was advised (not generally something I'm good at tbh) in terms of getting the right position. I think the idea is to stretch the spine so that the needle can pop through more easily...
I felt no pain at all. I felt a sensation from the needle at some points I think. But honestly no pain. I like to ask the question, 'Why' almost all the time so I can understand things more easily... Afterwards I drank water and lay flat on the bed for a few hours. In fact I slept but I was in hospital at the time.
Whilst I was having the Lumbar Puncture, the doctor asked me, 'had I fallen asleep'. To which I replied, ' no I've done as you asked and I'm staying as relaxed as possible but please crack on and hurry up'.
The second time was pretty much the same. No pain either time.
I hope this helps at least one person 😊🤗