Hy, For The Last 3 Days I Have Been Having

Hy, for the last 3 days I have been having some unusual symptoms. My nipples have turned a dark brown colour and are really sore, I am constantly feeling sick after eating and gone off certain foods. The most worrying one is I am forever going dizzy; whether I lift my head or stand up. I have taken 2 pregnancy tests which have both come back negative.