Back/leg pain when standing and bending

Patient: Ever since I was pregnant I have had lower back (buttocks) pain focused on left side. If I stand to long it starts to shoot a numb/burning feeling into my leg/outside of my knee. It also gives the same pain when bending neck downwards. I have tried stretches but they don’t seem to help. My left hip also feels like it needs to pop to help relieve pressure from my back but when it does the pain is worse. Please give me a guide line on what to do. What kind of doctor do I see?

Symptoms: Burning/numbness that radiates from my left hip region into my leg. Gets really achy and painful when standing for awhile. Feels the same way bending over and bending neck downwards.