What Causes Sore Breast, Nausea And Light Headedness?

Hi,been having sore nipples for the last 2 weeks.also feeling nausea&slight headache but the nausea is mostly in the morning.i had spotting for three days then after 2 dayz i had my period&they came a day late.have taken two pregnancy tests but all negative.my ovulation day was on the 11th but had sex on 12th.could i still be pregnant??