Withdrawal method is not very reliable method of contraception
. Failure rate is around 5-20 /100 women in a year.
Your symptoms suggest pregnancy
. So please do pregnancy test. Small amount of brownish discharge could be because of old collected blood after spotting , blighted ovum
, or just a symptom of threatened abortion
i would advise you to do the Urine pregnancy test. if it is positive, you must see a doctor, who will advise you to do Quantitative B HCG -two times, within a interval of 48 hrs, to confirm that pregnancy is going well. If pregnancy test is negative, and you do not see your period within 3-7 days, then also you should see the Doctor. he or she will redo your pregnancy test, pelvic examination and USG.
If you are not ready for pregnancy, use either condom or oral contraceptive pills
. Your doctor will tell you all the advantages, and disadvantages of various contraceptives method appropriate for you.