west I have SPD too, had it since about 16 weeks, sounds like that is what you are describing.
Have a look at this website - https://www.pelvicpartnership.org.uk/
I find it worst at night - turning over in bed is really hard, and when I have to get up it's agony, especially putting the weight through one side.
I find water helpful (but getting in & out of the bath is difficult!), heat packs, try a pillow between your knees at night too.
It's worth mentioning to your midwife & see if you can get a physio appointment - although saying that there's not much they can do. They gave me a support belt but I actually find it makes it worse. Some of the exercises have been helpful, and I find an exercise ball one of the most comfortable places to sit.