thyroid?!

So I'm 20 years old. The last few months I went from 160 to 236 pounds... I seriously thought it was just me not eating right. No matter what I did I keep gaining weight. I finally went to the doctors and I was told it was my thyroid... I never thought this would happen! I have an appointment coming up for treatment options. My question is, has this happen to anyone else? If so honestly will I be able to loose weight? How fast? I'm seriously so worried I'll never loose weight. Pleas and thank you!!!!!!