Help!!! Bfp after 4 day period??

Hey ladies, was ttc this cycle had been testing all the way up until I had received my expected period a day early. I had a medium/ heavy flow from 3/31 to 4/3. I have been feeling extremely nauseous and dizzy and just not myself, last night at work I absolutely had to call someone in. I decided to test just on a whim and received a bfp immediately. I'm so worried and wondering if this has happened to someone else?!