"It causes you to ovulate. It's more or less a fertility pill."
This is incorrect! Provera (medroxyprogesterone) is not a fertility drug. It is a synthetic hormone (progesterone). If you have amenorrhea (lack of or inconsistent periods) it is likely caused by low levels of this hormone. So what this drug does is what your body would normally do if your hormones were normal:
Provera thickens the lining of the uterus and (in most women) facilitates the increase of other hormones necessary for ovulation. Progesterone does not cause ovulation; estrogen and other hormones do.
When you stop taking the Provera, the fall in progesterone levels causes the uterus to shed its lining and menstruation occurs.
Doctors prescribe it to women who are trying to conceive if they don't get a normal period because it facilitates a course of events in the reproductive organs that *should* cause ovulation.
If you are trying to get pregnant and have been prescribed Provera to induce menstruation, it might be helpful for you to pick up some ovulation monitoring kits. You can get one at the drug store that measures LH surge (a urine test). After the first day or two of Provera, do the test a couple times in the next few days to see if you are ovulating. You should ovulate 24-36 hours after the LH surge. Get to it with your sperminator when that LH spikes!
Another type of ovulation monitor is the saliva microscope. They're cheap ($30) -- you can order them online. They do not measure the LH spike; they measure an estrogen spike. (Both hormones spike when you are about to ovulate.) The estrogen level spike preceding ovulation lasts a bit longer and begins a sooner than the LH spike, and you can sort of measure it by observing your saliva in the microscope each day.
If you have your period 2-7 days after your last dose of Provera, then you are not pregnant. If this continues to happen every month, you might have problems with other hormones and your doctor will probably put you on Clomid, which is to stimulate ovulation particularly. In fact, you'll probably be on both because they work together to get all your ducks in a row.