Generally for most folks this shows up in the third trimester, though if you had a it in your previous pregnancy, chances are good it will show up again (and earlier) in your following pregnancies. For most people this shows up as a sharp, shooting pain in the region of the pubic bone. See the thing about the pubic bone is its actually a joint, there are two bones that meet at what we think of as the pubic bone, and like any joint, there is connective tissue that holds the joint together.
Because of our good friend relaxin, connective tissue in the body is softening over time the course of the pregnancy. As baby grows, added weight is also added to the pelvis which puts strain on this joint and for some folks this ends up causing pubic symphysis dysfunction. It will usually show up one of two ways 1) when doing lunges or after long walks or exercise where legs are going forward and back or 2) when opening the knees away from one another in things like rolling over in bed.
Wisdom and insight with a dash of humor to help guide you on your journey through motherhood.