Thank you getagoldtoof - she's pretty much recovered now, just had the odd tired/achy day which is a miracle compared to how she was - she used to scream with pain crawling up the stairs at 3y (she wouldn't let me help her as she was a 'big girl' - btw the GP said that was normal toddler behaviour 
).
There's a picture of DD2 on my profile just before she nursed - you can see the pain she was in just from her eyes and how white she was (she would visibly blanch when in very bad pain). I still can't believe she is in remission! We are very very lucky.
She's now 4y 6m and is almost at the end of bfing - she nurses about once every 1-3 weeks (just enough to keep me on my toes and so that I think each time she does nurse it's her last).
I'm so grateful I have been able to nurse her for as long as she has needed me and I will continue to allow her to nurse until the point where she decides she's had enough (or her oral development puts paid to it!).
I realise it's not for everyone though (especially as she's the size of a 6y - HMS children are often very tall) but for all children every feed counts so be proud of however long you and your DC nurse for 
.
BTW please trust me when I say I have had times when I have had it up to here with bfing but if I can't do it then I have postponed and nursed later when I was in a better place (or just distracted myself while I fed if the child/baby's need to nurse was greater than my need to run out the room screaming 
).
We all have days when we just want to stop bfing/nappy changing/the constant incessant touching/jumping on feet and just have some personal space for once (or maybe even have a wee without an audience who are treating it like an interactive modern art installation
). Don't let the little whatsits grind you down....