Are you bleeding heavily or is this minor amounts of blood? If you are bleeding heavily and cannot get in to see your doctor, then I would recommend finding another doctor that can see you. Have you been on birth control at all... ever? If you took any birth control at any time, it can potantially throw off your cycle for a long time. You could possibly have a hormone imbalance which causes the irregular bleeding. Or there could be something else wrong. It's really hard to tell. But I would certainly say that if you are bleeding heavilly and if you start to experience any other nonperiod related symptoms to go see a doctor immediately. If things get worse and no doctor can get you in, then go to the emergency room. They will always see you there.
And of course, avoid stress, eat healthy, get plenty of water, and I would say stay away from tampons and douche until you are sure there is not something wrong in there.
Good luck to you!