Gland Disorders Forum - Frustrated About Hypothyroidism

I am a 17 year old female, who went to the doctor because of bad menstrual cramps and excessive bleeding. I was diagnosed with dub and put on birthcontrol pills (trinessa), but after a week they took me off because of depression that start around the time I took the pills. I have a history of depression, but have been fine for over a year and suddenly got really bad when I was taking the pills. The doctor told me to stop taking the pills and to come back for more bloodwork. After getting blood drawn three times the doctor came to the conclusion that my thyroid levels were off giving me slight hypothyroidism. The doctor said this was probably what was making my menstrual cycles so painful, and said that my thyroid problems was also what was causing the depression and making me slightly anemic. Today I got a thyroid ultrasound and they found a small cyst on my thyroid.

What is confusing me is the treatment they are giving me. For the anemia I am to take ferrous iron they perscribed and vitamin c with it. And they want me to go back on the birthcontrol pills. I argued with the doctor to change the brand of birthcontrol, in case it was the pills and not the thyroid causing the depression, and now they have me on trivora. But, if the doctor is so sure that it is my thyroid causing all these problems, why aren't they doing anything about my thyroid?? I go back to college in the end of august, and am afraid of having the same symptoms of an underactive thyroid that made me take a year off already--the fatigue, depression, being cold all the time as well as other symptoms such as hair falling out. So if my thyroid is making me so sick then why are they treating everything else besides the thyroid????

Sorry if that was confusing, i'm just a little confused and frustrated. I am going to talk to the doctor tomorrow and see if she can enlighten me, but right now none of this really makes any sense.