Hi I Have Been Having Pain Around The Waist Region

hi i have been having pain around the waist region especially when i get involved in walking long distances or doing work that needs a lot of movement. the pain mostly affects the left leg and side.when i strain more in moving the pain affects the whole waist part. i went for x-ray and scanning but nothing was identified.the problem started when i was stung by an unknown sea creature that was perceived to be a gelly fish but were not exactly sure.i had spinal pains when stung and no body movements.i was treated and got well again but since then i started experiencing the waist pains when i participate in alot of movement activities and which involve bending and my legs get numb quicker than normal when i sit. please help me identify the problem.