Good Afternoon :) According to your history you may be suffering from inflammation of you lower back joints and ligaments. It could be due to Coccalgia (Damage to the tail bone). You may take pain killers like Diclofenac
for a week to relieve the pain. Also eat diet rich in fibre like fresh fruits and vegetables which prevents constipation
, which can also be a cause for coccalgia. You may also consult your Orthopaedician if the pain increases and do as recommended.