Hello, I Am Very Worried. I Have Been On The

Hello, I am very worried. I have been on the birth control pill Tarina Fe 1/20 for about three months now, I take it everyday, but not at the same time every night. It's supposed to be at 9pm but sometimes, I do it at 10pm, or even 11pm. However, I never missed a day. On my third week (April 6th) of the pill I started spotting brown.. it confused me because I wasn't expecting my period until this week. However, the spotting is continuing and I still haven't gotten my period this week. I am very concerned because I researched it up online, and it says it may be because of implantation bleeding. Could I possibly be pregnant? I took two home pregnancy tests and both result in negative. I however don't know if I did it accurately. Could it be side effects from the pill? I just don't understand why I spotted on the second week of the pill and am now not getting my period when I am supposed to.