Conception. Technically; as soon as conception occurs one's body will begin changing on every level. Some women can even tell the moment of conception; believe it or not.
Negative test? If an hpt is negative it's too early for symptoms to be reliable. No reliable symptoms happen until long after a pregnancy test would be positive. Good luck!
Missed period. At the time you miss your period. Classic pregnancy symptoms can include: tender or swollen breasts, nausea or vomiting; lack of a period; increased frequency of urination; headaches, insomnia, fatigue. Moodiness, mild cramping, food cravings; passing gas; enlarging waist line. Etc. There may be an increase in white vaginal discharge.