To determine the date of conception based on your last menstrual period, you can use a few methods. First, calculate your estimated ovulation date by subtracting 14 days from the first day of your next expected period. In this case, if your cycle is typically 28 days long, subtracting 14 days from January 26th would give you an estimated ovulation date of February 11th. Keep in mind that this is just an estimate and may vary depending on the length and regularity of your menstrual cycle.
Another way to estimate conception is by using an online ovulation calculator or fertility tracker. These tools take into account factors such as the length of your menstrual cycle and provide a more accurate estimation of when you likely conceived.
However, it's important to note that these methods are not foolproof and can only provide an estimation. The most accurate way to determine the date of conception is through medical tests such as ultrasound scans or blood tests. If you suspect you may be pregnant and want a precise answer regarding the date of conception, it's best to consult with a healthcare professional who can guide you through the necessary tests and examinations.