Hi, and thanks for your medical question on eHealth forum
If you have been late in taking pills and use the withdrawal technique, then there are chances you could be pregnant as the withdrawal technique is not 100% safe. Also, a certain amount of brownish discharge is expected in pregnancy. Take a pregnancy test and see.
The other possibility is that the periods are delayed because of an irregular pill intake. Wait and see for another few days if the pregnancy test is negative. The other causes are hypothyroidism, polycystic disease of the ovary, anemia and poor diet.
A confirmed diagnosis cannot be made on the internet. Please consult a gynecologist.
Hope this helps. Take care!