Brown discharge while on Nora-be?

Izadora
Hi! I'm 19 years old and I'm on the mini pill Nora-be because I'm currently breastfeeding. I gave birth on Jan 9th and started taking the pill after my 6 weeks follow up appointment at the ob/gyn (Feb 20th). After that my period has been really irregular. In March I got my period 3 times and on March 29th I missed a pill. I got my period on the next day (it was lighter than usual) so I started taking the pill again. I did what I read in the leaflet and did not have unprotected sex for the following 48 hours. After that I only had a couples of days of brown discharge on April 10th and 11th and today (April 20th) I had minimum bleeding ( not even enough for panty liner) and the brown discharge showed up again. I took a home pregnancy test yesterday and it came back negative. Should I worry about pregnancy? Could I have something serious or is brown discharge normal on mini pills? Did any of you guys have a similar situation?