Hi doctor I'm ver concern I have had sexual intercourse with my husband two weeks straight with.no protection I usually get my period every month on the 18th but I'm bleeding very light on today which is oct 15th why is this

While perhaps on the 18th you normally get your period, it is hard to believe it is always on the 18th, that would be rare, esp since some months are longer, some shorter. So always on the 18 would not even be a regular period

Most women are a few days early some months, and a few days late some months, at times they may even miss a month. There is no real NORMAL for everyone.

But it means that you started your period early at this point, when the period is over let us know if it was a normal one, or if it was always light and perhaps only lasted 2 or 3 days.