Pink or brown spotting
may be due to hormonal imbalance, caused by birth control pill itself, pelvic or vaginal infection
, stress, cervical polyp
Here, chance of pregnancy
is quite rare by using birth control pill and condom.
I suggest you to consult with gynecologist for pelvic examination to rule out other underlying pathology (if any). Till then, maintain genital hygiene and avoid mental stress. Good luck.