When you sign up to be a part of any study, the researchers usually go over these details very carefully. Subjects usually know they may not be getting the real treatment.
In the most ethical practice, patients are unblinded at some point. This means they are told which group they were really in. Any patient who wasn't treated but still has pain or symptoms then has the option of seeking additional treatment.
It sounds like you were in the control group (untreated), but you were unblinded after six months. You very likely agreed to this, or you wouldn't have been included in the study. If you have any doubts, ask to see the paperwork you signed at the beginning of the study.