Birth control

I started birth control for the first time ever May 25th. I’m now mid cycle not expecting my period till around the 26th and spotting black blood/ dark discharge. I also have stomach cramping that is accompanied by chills and my stomach gets upset after eating almost anything. Are these normal side effects to taking birth control? I was scared it could mean I’m pregnant but it would be to soon to test. I take a pill once a day before bed.

Tmi;

I should add the stomach aches and chills makes me have diarrhea and I have wanted to vomit.