I have lower back pain and AF like cramping since 2DPO and today I am 8DPO, just like you it is very unusual. But on 6DPO and 7DPO I had a sharp AF like cramps for 20-30 mins and they would stop around the same time. Today I felt the same but less painful. I will test tomorrow and see how it goes. AF is due on the 3rd. I did some research and lower back pain is one of the most common early pregnancy symptoms. Hopefully we conceived this month.