I had this too! But my OBGYN is awsome and immediately knew what it was, however, the cure took all my WILL and months to cure it. Your sciatic nerve runs right down the butt and vagina and it is pinched. Years ago I was very limber and thought I was 'just' getting older and that is why I could barely stretch my head down while sitting open legged on the floor - well NOT old age, it inflammed sciatic nerve making the muscles around it contract. It took months of stretches, yoga and basically every day concentrating on stretching those muscles and constantly massaging them so I can now put my head on the floor like I used to in a full stretch and NO more shooting pains. Nerve/muscle pain is very common and chronic and most people are not able to put up with the exercise regimen to fix themselves and live with the pain for the rest of their lives on meds. It takes the WILL like the hardest diet ever or like when quitting cigs, it takes discipline to stretch everyday when you barely see any improvement to keep going and going, but eventually the muscles give up and let you stretch a little further. Good luck.
I had this and my Dr told me it was round ligament pain. Your body getting ready for the baby.