The first thing I would think of getting tested for is STD's (assuming you've had at least one partner). Your local health clinic or Planned Parenthood clinic can help you get tested for free.
If it's not that, thyroid disorders can cause missed periods. If that's the case, you would need to start treatment. Is there a clinic in your area you can go to for free to get checked? Catching thyroid issues in time can mean getting treated & starting normal periods again. Putting it off for too long can unfortunately lead to infertility. I'm not really familiar with what the timeframe is. I do know people who have gone up to 3 years without getting their thyroid treated & they were able to get pregnant afterward with the help of fertility treatments, but I'm not sure how much different factors can contribute to it.
It's a simple blood draw to diagnose. There are several types of thyroid disorders & while some are more likely to cause Amenorrhea (missed periods) than others, any of them can cause that.
I'm not sure why you were told that BCP would keep you from ever getting pregnant. You can go on it for several years & then stop it a few months before you're ready to start trying. Some people just need to be on it for 6-12 months to regulate their hormones & then their body functions normally.
Here's a link to a list of common causes for missed periods (please do go see a doctor, though. you really do need a diagnosis since treatments for some possible causes can end up making you worse if the cause is something else.):www.mayoclinic.com/health/amenorrhea/DS00581/DSECTION=causes