Provera is not an ovulation stimulator. In fact, Provera inhibits ovulation. However, when a woman stops taking Provera, ovulation should re-establish itself spontaneously. If Provera doesn’t help indirectly provoke ovulation, you might try a direct ovulation stimulator such as clomiphene. According to the data you provided and considering that you are overweight, experience an irregular cycle and lack of ovulation you could be tested for possible Poly-cystic ovarian syndrome (PCOS). You can consult your gynecologist for diagnostic tests and to request help in identifying the real cause for sterility.