Pos to neg over night???

I tested yesterday about noon and got the faintest positive and the again first thing this morning and it was a very clear negative, I plan on testing again because I have been feeling nauseous everyday for the past week off and on and have nearly thrown up a few times, my boobs have grown a full cup size and are sore, I’m broken out not badly but I have a few zits and typically have clear skin, if anything gets over whelming I get dizzy and light headed, which has never happened to me before, and I did have mild cramps a for a few days, only thing is is my periods still 5 weeks away because I’m on a 3 month pill