What Causes Delayed Periods After Discontinuing Birth Control?

I am 19 years old and i have been on birth control for 4 years and i went off it almost 2 months ago and now im having problems. i still haven`t started a real period i have had a light stringy brown smell sour discharge for about 8 days ( i should have started my really period 8 days ago) and im wondering whats going on with my body if its just a side effect of not being on birth control? or something else?