What’s going on ..

The last time I had my period was the week of December 6th I spotted in the morning on January 31st just wiped and it was gone. Since then I have taken 4 pregnancy test (weeks apart) all four have came back negative 😩 I was on birth control from the months of oct-December but those last days of December I kept forgetting to take them. I’m not sure what’s going on 😩