Hallow Dear,
If you are regular on your birth control pills, you are well protected against the
pregnancy. The last 7 days sugar coated pills are not necessary for birth control, they are tonic pills, included just to keep you habituated in taking the pills. These pills give you more than 98% protection against pregnancy.
However, the pull out technique you are using is very unsafe method of
contraception. Before semen ejaculation, there is always a discharge of pre-ejaculation fluid (precum). It slips out of penis without knowing. Precum does contain some amount of sperms which are capable of fertilizing an ovum. However, since you are so regular on birth control pills, you may enjoy full complete intercourse without pull out technique.
If you have not missed your period, you need not worry about the pregnancy. Missing a period is the first cardinal symptom of pregnancy.
Brown spotting is just exit of the old blood (mostly menstrual) from the
uterine cavity, it is never a symptom of pregnancy.
I hope this resolves your dilemma.
Dr. Nishikant Shrotri