Me and my boyfriend had sex(Sunday)and the next morning( Monday) I felt fine but the following day(Tuesday) I felt nauseous , the next night (Wednesday) I started spotting , the next afternoon (Thursday ) I took out the tampon and there was barely any blood , also I've been feeling sick to my stomach, tenseness in my breast and areoles, light headed ,heartburn at rare times .. I don't believe that I'm pregnant but I'm not 100% positive any other reasons or information about these symptoms ??