What Causes Brown Vaginal Bleeding Along With Burning Sensation In Stomach?

hello so I bleed a week before I was supposd to and it lasted one day then a couple days later I had brown in my underwear then it stopped so I took a two test both negative, im supposed to be on my period now but im not. could I have taken the test to early? I have a slight burning feeling in my stomach and I have been feeling quite lazy latly. I am 23 and have had a normal period all my life