Back pain and painless lumps

Patient: Hello,I am a 22 year old mother of 2 .i have lower back pain for 3 years since i delivered my first baby, it was a normal delivery without any medications for pain. I can’t stand or walk for more than 20 minutes, if i do i get a severe burning pain in my lower back and it feels impossible to bend. It goes away if i rest. And i also have two large lumps on both sides of my lower back but they are painless even if i touch them. I am just concerned if the pain is related to these lumps? Which doctor should i see for this pain.Thanks.