Okay, so first: in Steve's defense, the symptoms you describe CAN be life-threatening. However, you are only 20, and you don't have other medical problems, so that makes the likelihood that your symptoms are evidence of either an acute heart attack, or congestive heart failure a little less likely.

Plus, you're still standing. :)

So let's dig a bit deeper. You're taking Metformin, which means you're either mildly diabetic, or you have polycystic ovarian syndrome, or perhaps you're trying to get pregnant, though THAT seems unlikely, given that you're on Yasmin.

I doubt it's a medication side-effect.

Probably not asthma either, since that usually doesn't come on at your age, and as suddenly.

So, let's break it in to categories: first, intrinsic pulmonary causes: not much comes on this quickly. It COULD be a disease called sarcoidosis, but that's about the only intrinsic pulmonary disease off-hand that you'd fit. Second, autoimmune (aka rheumatologic): it could be something like lupus, or Wegener's, or rheumatoid lung. Again, these would be a bit unusual to present with breathing problems (although lupus is pretty common in your age group). Third, let's try infectious: you could have an acute infection, like a pneumonia of some sort. Perhaps you've had fevers? Coughing? Bringing up any mucous? You could also have a weirder infection, depending on where you live, like coccidiomycosis, or histoplasmosis. And lastly, cardiac: you COULD have heart failure for some reason. Perhaps, now, you've got a problem with one of your heart valves (like mitral valve prolapse), and now your heart can't pump blood forward very effectively, so the blood is getting stuck in your lung.

So, that's just a brief, quick and dirty list of a few things that could be wrong. Unfortunately, most of them are not particularly benign, but fortunately, most of them CAN be treated, often to the point of cure. The bottom line is, GO SEE YOUR DOCTOR! At the least, you should have a chest xray to see what's going on.

You COULD, if you wanted, google all those diagnoses that I suggested... but that might be a little alarming. Based on the info you've given me, I have no idea what it is... but I would say that something in your heart could be the most likely. And you should have it checked out.

And when you do, let me know what it was. I'm intrigued.

I hope all of this helps. If it scares you a little, that's okay, because it will make you go to the doctor. And that's who should REALLY be advising you about all this!

Good luck.