Could you be pregnant if get a period at all one month and then the following had an abnormally light 3-day but four negative HPTs?

While it is possible to be pregnant and still experience light bleeding or spotting during your expected period, it is unlikely to be pregnant if you have had four negative home pregnancy tests (HPTs).

Conception usually occurs during the fertile window, which is typically 10-14 days before ovulation. If conception does occur, the fertilized egg implants into the uterine wall about 6-12 days after ovulation. This process can cause some implantation bleeding, which is often light and may be mistaken for a period. However, if you are truly pregnant, your HPTs should detect the presence of the pregnancy hormone (human chorionic gonadotropin, or hCG) in your urine.

Here are a few reasons why you may have had an unusually light period followed by negative HPTs:

- Early pregnancy loss: It is possible that you experienced a very early pregnancy loss, such as a chemical pregnancy, which occurs when a fertilized egg fails to implant or implants but cannot sustain itself. This can cause light bleeding or spotting that resembles a period.

- Hormonal imbalances: Changes in hormone levels can affect the length and heaviness of your periods. Certain conditions, such as thyroid issues, polycystic ovary syndrome (PCOS), and perimenopause, can cause irregular periods.

- Stress or lifestyle changes: Stress, travel, and significant changes in your routine can temporarily disrupt your menstrual cycle, resulting in light or irregular periods.

- Medications: Some medications, such as birth control pills, hormonal treatments, and blood thinners, can affect the nature of your periods.

It's important to note that home pregnancy tests are generally accurate when used correctly and after a sufficient amount of time has passed since conception. However, if you have any concerns or irregularities in your menstrual cycle, it is advisable to consult with your doctor for further evaluation. They can perform a blood test to detect hCG levels or order additional tests to determine the cause of the light bleeding and negative HPTs.