I am on birth control and had my last period from the 4th to the 8th. today is the 19th. for three days i have light brown discharge and today i am having very dark brown discharge. should i be concerned? could it be pregnancy?

Mid-cycle spotting is not uncommon due to a normal drop in hormones. If you had sex since your last period, do a home pregnancy test if you miss your period by 4-5 days. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully. If you do not wish to be pregnant, use contraception all the time, every time.