Anyone have lower back pain, hip and knee pain in early pregnancy?

I’m 7 weeks pregnant and last night I had horrible lower back pain that radiated to my hips and knees. I am so confused as to why I’m experiencing this pain so early on in pregnancy. The doctor told me that it could be normal. I am a burn survivor. With my injury, I had all of the fat cut out of my left leg due to an infection so it’s literally just skin on muscle now. I also have DD size breasts that have got much larger, adding extra weight on the back, so thinking maybe my body is just adjusting poorly to these changes? I’m terrified of another miscarriage.. 😣

This little one is due on my birthday, they have to be ok! 😣😭