What is wrong with me

So I've had bleed three times this month. Two times was right after sex and then today. All three times it was very light bleeding (first two times lasted maybe an hour, today it was almost all day but very very light and then it stopped). I have had soar boobs and been nauseous for about a week and a half. Now I am always hungry, I took a pregnancy test today and it came back negative but I wondering if it was inaccurate. Does anybody know what this could mean?