My period is 3 weeks late, which means i would be 7 weeks pregnant yet im still testing negative to hpt. is there any other reason for late period?

Possible reasons...: In a woman with regular periods, some causes of a late period include: excessive weight loss or weight gain, increased exercising, emotional stress, having an illness, traveling, medicines (like birth control pills), hormonal imbalances, etc… seeing a doctor is a good idea if symptoms are persistent, recurring, or worrisome. Pregnancy is the common cause of a missed period, if sexually active.