Google the Pelvic Instability Association, there is also a Facebook page for updates and latest research links.
It's not something you have to put up with, there are things you can do to manage it, so don't be fobbed off by a doctor or physio. Go to someone who is experienced with pregnant women. Find an acupuncturist who specialises in pregnant women - I was just telling a GF tonight about how I hobbled into my acupuncturist and then walked to the nearby shops, taking a couple of minutes to realise I was walking without pain Of course, it came back within a week, but I could manage it better.
A GF of mine is a founding member of PIA and has had many bouts of surgery - most sufferers don't get to this extreme.
Between pregnancies I managed it with regular osteo and yoga, then in the 2nd pregnancy did yoga, regular osteo and about 3 acupuncture sessions.
I had some bad experiences with physios, so you won't find me recommending anything other than an osteo I posted about it after DS birth on the ABA forum after being told by a physio that it was being prolonged by breastfeeding, and a lovely, knowledgeable lady referred me to a great clinic in Melb. There is NO evidence that breastfeeding prolongs SPD, so don't let anyone tell you that.
I can live a pretty normal life now, even though I've had SPD since my first pregnancy in 2005 - I ride horses, I surf, I do firefighting, we now live on a farm, I ride bikes etc. I just manage it and avoid certain actions. For instance, I know I can't split wood without paying for it - my neighbour is the same, but her husband bought her an electric splitter, so there's no guilt now that she can't do it (she's like me and feels very much like she wants to be part of the action!), and my DP prefers to say that I'm 'weak' He still doesn't really get it - he thinks that if I stretched enough it would go away