Thank you for posting on HCM
From your description, pregnancy
is possible and another possibility is post birth control side effect. If you had been having unprotected sex, then the chances of pregnancy are likely. Early pregnancy test can come never especially if doing a urine pregnancy test. My advise is to do it at a hospital where your blood sample can be collected and dosage of beta HCG
done. A pelvic ultrasound
will also be useful and can also rule out pelvic abnormalities such as PCOS, endometriosis
that could be the cause of your abnormal bleeding.
Brownish dischage could signify implantation
bleeding (as a result pregnancy test will be negative as still early) but also signify a pelvic diseases which will need to be identified by a gynobs.
Hope this helps and wish you the best