I sympathse if it is SPD. i was diagnosed this at 20 weeks with DD, it got gradually worse and in the end i ended up having to use crutchs to get about on. I had physio, and they gave me a beautiful looking big wide supposrt belt (supposed to hold the pelvic bone together and reduce movment) i felt this did help me a lot. Also went once a week for the last two months to an osteopath. Dont know if it really helped completely but then who knows how bad it may have got if i hadnt gone to him....!My SPD didnt have time to go, i still had it while breastfeeding up to when DD was 5 mths, then i became pregnant again...more relaxin hormone for me, more SPD i fear!!
Some other tips i picked up;
wear a silky nightie to bed, tell your partner not to get excited, its for helping to make it easier when you turn over!!
And def sleep with a pillow between yr knees.
If you have to drive, its really good to sit on a plastic bag, then you just 'swivvel' on it when you get in and out.
As much as possible keep your knees together, thus avoiding moving the pelvic bone too much.
Try sitting on one of those big exercise/pregnancy balls, as long as you keep your balence, they are a great support!
Definatley get a support belt, not the thin ones you see on ebay, they were rubbish for me, but the big wide ones, much comfier, or get your MF or Physio to cut you a length of tubigrip. Use this to pull under your bump but around the pelvis area.
One thing i did, when i went shopping at a local shopping centre i hired one of those shop mobility motorised chairs!!!! i was a bit at first but i took a friend and we ended up having a right laugh, and it meant i could stay out shopping a lot longer than i would have if i had had to use the crutches!!
Hope these tips help and that it doesnt get to bad for you, Minkimoo, and anyone else, its not nice and can really put a dampner on things.... But it does subside......eventually!