If you are overweight does provera (medroxyprogesterone) work to start your period after having a child?

Often, yes: A big factor in when you get your period after delivery is whether you are breast feeding. While the typical time for menses to resume after delivery is about 6 weeks, breast feeding delays this. If return of menses is unexpectedly delayed, a pregnancy test (perhaps others) should be done. Then a Provera (medroxyprogesterone) challenge can be tried. Being even moderately overweight should not affect this.