Severe lower back pain. Will help me?

Hii I have severe lower back pain from last 4 months i did not fall neither I had any injury, it started all of suddenly after a long travel by car ,since than the pain is same, I got some blood test done ,I have severe deficiency of b12 or vitamin d and I am anemic also iron is also low, I have hypothyroidism as well , I did hot pack on back it gets relief of some days but again it back the pain is still a lot I have light swelling on right upper thigh with pain since 2 months there is no redness but pain is there. Is there any connection thigh pain with back pain please tell me , currently I m taking b12 vit d supplements, could you please tell me what can be reason of this back pain and which doctor I should consult nuerologist or orthopaedic for back pain Please help me out it's humble request I asked about this so many times hoping this time someone will help me