I had SPD with my last baby but haven't had it yet thankfully.
When I had it, it definitely felt as though my pubic bones were tearing apart... it was a horrible, burning sensation. I also had pelvic instability which caused me sooooooooo much pain when sleeping.
The SPD was definitely the worst thing about my last pregnancy. I couldn't walk far without feeling like my pubic bone was going to break; I couldn't put my underpants, pants or anything on that involved me stepping into them without sitting down.
Let your OB or midwife know at your next appointment and see what they have to say. I hope it eases up for you soon.