Severe pain in the left nipple only sudden now for more than an hour only area that hurts. i am trying to conceive but only 16 days since last period.

Wild hormones OK!!!: At 16 days from your last period the hormones are circulating in abundance. You may have ovulated, so progesterone is rapidly increasing. Estrogen has been at a high level but has decreased from earlier in your cycle. The hormones in the brain are making adjustments so that your body will be ready to receive a fertilized egg. The breasts are hormone sensitive and do react to the changes.