So sorry to hear you've SPD - I was diagnosed at 27 weeks and have been signed off sick ever since. This is my first baby and I've heard it can be worse and start earlier with subsequent pregnancies
I was referred to a physio who recommended pelvic floor exercises, pelvic tilts and a stomach strengthening exercise (NOT sit ups) - you just suck your tummy in as if you're trying to fit into small trousers or having you photo taken! You breath out at the same time. I do about 25 quick reps or 5 slow reps (hold for 5 secs) of each 2-3 times a day.
There is also a thread on the tri 3 board which describes the exercises much better.
The physio also gave some other advice - try and keep you legs together when doing things like getting in and out of the car / bed. She also said to do movements, particlularly turning movements in small stages - so don't stand and twist at the same time - stand up, wait 2 secs then turn slowly, always keeping your feet and hips in line - move by making small steps rather than a big twist.
Another point is not to do anything for too long - standing, sitting etc. At first I totally rested, but the 2nd GP I saw recommended trying to keep mobile. Now I try and intersperse sitting with a bit of pottering about - every time there is an ad break I get up and go the kitchen.
I've also started 'water walking' - just walking along the bottom of the pool. I do the pelvic and stomach exercises in between. I would only do this if it doesn't hurt though - I find the weightlessness in the water really helps (particularly now I'm 34+5).
I have found by doing all the above it has improved slightly - so it's not a miracle cure, but I think perhaps I would have got a lot worse if I hadn't done exercises etc.
Before I got SPD I used to walk a lot with a bag over my shoulder - I think this may have made the SPD worse. Now I have to take it really easy and try not to carry anything heavy, particulary on one side only.
A colleague at work also had SPD (with her 2nd and 3rd pregnancies). She was really bad with the 2nd one but for the 3rd spotted the signs early and got a support belt / tubigrip. She said it made a huge difference.
I tried the belt and it hasn't helped me much but it's def wortth a try. The physio dept should supply one, so I think you should push your GP/midwife to refer you to physio asap. They'll also be able to show you how to do the exercises properly.
Hope this helps you - and sorry for the MASSIVE post!
Gemma x
