Confused

Hi, please can someone help me.

A couple of days ago I took my last contraceptive pill and had noticed that I’d been bleeding a little bit and it was brown. Sometimes there is brown discharge and then when I wipe it’s o occasionally red.

It’s very light and my usual period is heavy and lasts up to 7 days. The bleeding is currently still happening.

I took a pregnancy test on Saturday and it came up negative. What is happening?