Back ache - Early pregnancy symptom? Help!!

Can you help me? I've had really strong back ache pretty constantly for the last 3 days now. It feels like strong period pains but I'm not due for another 3 days and have had no bleeding. I was certain I was getting my period but have had nothing. My tummy feels bloated and I have a pinching sensation below my tummy button. I'm 11dpo. Did a hpt today but bfn. Has anyone ever experienced these symptoms and got a bfp? Or is this more likely to be af symptoms? I would appreciate your opinions. Thank u!! Lizi