I am on the pill i started my last period on sep 28th and finished on oct 5th i started to bleed again on oct 19 and blead till oct 31st it was brown ?

Breakthrough bleed: Sounds like breakthrough bleeding which occurs when you have bleeding at unscheduled times while on the pill. Brown is simply old blood that has been sitting at the back of the vagina. Often things get back to normal the next cycle. If not then schedule a visit to discuss changing brands or changing birth control methods. This is very common. Other than being annoying it is not dangerous.

May be normal: Several questions would help answer your question. Are your periods often irregular and do number of days bleeding vary? Have you ever had brownish discharge as part of menstruation? Since you just started the pill (oc), initially irregularity and changes can be entirely normal. Give it another month to see if period starts regulating normally. If any doubts, call your gyn that prescribed the oc.

Breakthrough bleedng: Some low dose pills allow spotting or breakthrough bleeding to occur. If you've taken other meds recent, be concern about failure. If one time event, np. If recurrent, can double up on pill till stops(takes extra pk), take a pill holiday, or get a stronger pill. If still happens or reason for concern, get screen for std. (sex transmitted disease).