Hi, I gave birth November 16 and suffered from the same pain up until about a week 1/2 after. My entire bottom half was sore and my baby was only 6lbs. My doctor said it was just due to childbirth and pushing and pelvic bones going back to normal. Congratulations and hope you feel better soon.
When delivering vaginally, your tailbone flexes back to allow room for baby to exit. It is common to have soreness. You can alternate heat and ice on the area. As far medication, ibuprofen is best for this type of pain.
My friend had the exact thing happen to her. She said it was from labor and pushing her baby out. She had it really bad, but it got better.
I have it! Gave birth one week ago, 9,7lbs! Im in so much pain, i can barely move, and getting up from a sitting position kills me. I just started to use a heating pad. Seems to help. I never had this with my first one....although i did tear with that one, so i had that pain to deal with. But this back pain is no joke! It hurts!! Good luck ladies!