It sounds like a hormonal imbalance. You may want to see a doctor for an exam and a full work up, including blood tests (your female hormones plus a complete thyroid panel). An ultrasound of your abdomen and pelvic area may also be helpful.
Symptoms are completely unreliable and the symptoms for 'pregnancy' are the same for PMS, stress, hormonal changes, illness, and so on. Since you are on your period, that means you are not pregnant, as long as this period is the same as it always is. When are you getting married?