I had SPD while i was pg with Em from about 30 weeks. I got a referral to the physio who really helped. I have heard that it can be worse in subsequent pg's. While I had SPD Sarah learned to walk which took some of the strain off me but I did learn to make use of the pram rather than carry her around. Don't have a bath as that will make it worse afterwards. ice packs r also better than heat packs.

See if you can get a referral to the physio as they may be able to manipulate your body back to what it should be. HTH