my period hasn’t came after birth & I took test they came out negative

So I gave birth on Oct 4th and I haven’t started my period yet ? My period were always irregular before I was pregnant due to my depo shot & I have gotten my period late when I was younger but I had took two test already they both came out negative and I still haven’t started my period I told my dr and she said it will soon I been having bad pains in my private part like lightning pains down there … how long did it take for you guys to start ur period after birth ???