I gave birth to my stillborn baby boy feb/13 everysince then i've been having pain in my lower back right side it feels internal what could be wrong?

Epidural/Spinal: Differential list is long : Possibly due to an epidural or spinal received during labor; streteching of lower lumbar spines and sacral nerve bundles due to pressure at delivery; direct damage to coccyx and innervation from pressure of fetal head during delivery; internal pelvis muscle strain, sprain, or tear; uterine myomas; endometriosis, retained products of conception( need D & C)