Hi, I have SPD too and I'm currently 35 weeks so in a similar situation, only mine started really early so I've had a bit of time to get used to it.
Be really careful with things like dressing - I tend to sit on my bed when I put my trousers on and fling them out rather than lifting my legs into them. DH helps me whenever he's around too as stepping into clothes is one of the most painful things for me.
When you have to have internals for the midwife/doctors tell them you have SPD and try not to open your legs too far - easier said than done!
Try a pregnancy pillow or a normal pillow between your legs. I find it difficult to sleep like that but it's a good way to relax and rest.
A support belt can help if your bump is too heavy but I didn't really get on with mine.
Don't step over things, lift anything heavy or stand up for too long, and try to move around if you're sitting for a long period - just change your position so you don't "freeze"
And take the painkillers you feel comfortable with.
Hope that helps a bit? There are some days when nothing helps and it's a bit disheartening, but it won't las forever :)