How Long Should I Take Othrotricyclin Pills To Regularise Periods?

I have been on othrotricyclin pills for regulation since I was 9. I am now turning 21 and I quit taking it January of last year. I only had 3 cycles (oct, Nov, and Dec.) since january of 2010. My dr recently put me bak on the pills and I just started my period for the first time since December. But im worried because it is really stringy and has a brown tint to it.