I would also ask you a few more
questions, like is this common for you to have irregular
periods, and how old you are. Irregular
bleeding is usually caused by failure to ovulate regularly which can be caused by many things: stress, weight changes, PCOS, polyps, peri-menopause, to name a few.
Give your doctor a call to get this all sorted out. Its UNLIKELY to be serious, but should be sorted out.
Good luck!