Hi Jas G,
If you don't have a gynecologist yet, I recommend seeing one. I'm naturally irregular too. I had to go on the pill to get my periods regularly but you've really got me on this one. Usually a light brown discharge before the period is normal.
Quoted from Dr. Alecskovski:
"The brown discharge a few days before the menstrual period is considered normal. Generally, it is due to the sudden drop in certain female sex hormones. The drop is expected in order to prepare the body for the start of the period. Occasionally, however, the drop may be so sudden and severe that the inner lining of the uterus may start to detach a little."
If your period doesn't come right after this and doesn't come at all, go get checked out. It may be nothing but it may be something entirely important.