Dear Jen,
It sounds to me like you need to be talking to some of the people you work with in the hospital! *smilling* The lack of periods alone , or the weight loss alone, might be explained away sometimes, but the combination of the two could signal something that needs to be treated right away (Hyperthyroid, maybe? Hormone imbalance?).
At 26 you're far too young for an early menopause (like I had), but it might be the beginning of an early onset perimenopause, and your OB/GYN should be able to help you determine that. My periods became extremely light in my mid 20s, and by my 34th birthday, periods were history all together. The same had been true (within a birthday or two) for my mother and grandmother, so it was a genetic thing in my case.
See if you can get some blood work done to test your hormone levels, and ask someone if this could be related to your thyroid.
Good luck! I know you'll get this straightened out.