With my first pregnancy, I managed to jar my sacro-iliac joint whilst bending down to pack boxes (we were moving house) at 34 weeks. Within 48 hours the pain had got so severe that I was bedridden. I managed to get to a prebooked midwife appointment the next day (my husband drove me but they had to get a wheelchair to get me across the health centre car park) where they referred me straight to a physio. The physio gave me lots of excercises, and support belt and a pair of crutches which I continued to need up until I gave birth at 42 weeks.
The area of pain sounds very similar - base of spine, right down to my buttocks. I'm totally not wanting to scare you with my story as I know my case was rather extreme, but rather to reassure you how beneficial the physio referal was. I literally went from being bedridden to, over time, being able to walk (very slowly) across a room without use of crutches, purely from perservering with exercises. I would advise that you push for a physio referal and hopefully you will be able to prevent the situation getting any worse.
That whole pelvic area is so prone to problems during pregnancy, mainly because of the increase in the chemical relaxin in your body during this time. It literally causes joints to relax and not hold together as firmly as they would normally, in order to prepare the body for what is needed during childbirth.
I hope you manage to get it sorted x
Archie Benjamin - January 2007
Imogen Sophie - April 2009