What Causes Joint Pain With Shoulder And Knee Pain After Delivery?

Hi I am into 6 months post delivery phase. I didn't take proper rest just after the delivery of my first son for almost the first 2 months, i was going for shopping, changing the nappy and taking bath of my son. For the first 1 month nothing happened and i was happy that i was healthy. But after 2 month i started having pains in joints, back, shoulder, knees, wrists. My first doctor asked me to do some test which includes RA Factor, ANA, CRP, Blood Urea etc and all came out negative or within the permissible limits. She also prescribed my HCQS, Etova P400, Dolo 650, Rantac 150 aprt from my regular Calcium intake. I didn't see any improvement even after 2 months of this interaction. So i consulted a new Orthopaedist who asked me stop taking all the medicines prescribed by my first doctor and advised me to take Vitamin B complex, Vitamin C, and calcium. But nothing does not seem to help me. I have been talking to some of the SLE patients recently and they suggested me to go for SLE test. I am kind of a bit confused now. Can you please suggest me what to do now. I am basically based in Bangalore.