Hi. I Am 27 Years Old. I Am 4 11

Hi. I am 27 years old. I am 4 11 and weigh 120 lbs, I am a full time pre school teacher and I teach Zumba fitness at least 4 times a week and I work out 5 along with weight training. I am on a strict diet and I lost weight pretty fast. I had pneumonia back in Novemeber and have not had my period since. I saw my gyno and he had me try to take pills to bring my period back which did not work so he sent me to an endocrinologist which took an mri and found that I have a small pituitary tumor 5mm. They are not concerned that is it cancer however because of it he sent me to a medical endocrinologist which took blood results and found that I have very low estrogen and I am post menopausal. I have horrible anxiety. I cant sleep. I wake up with hot flashes and sweat through my sheets. I have back pain and get dizzy. I am constantly hungry. I have not gained weight I actually lost weight but have noticed that my stomach is not as flat it seems to be bloating. My dr is starting me on a birth control tomorrow called lo ogestrel. What are your thoughts. I am scared. Is this dangerous. Is there a chance I may have cancer? Does this mean I'm at a greater risk of premature death? I really read too much into things online but these are things have I have read. What is true?