I noticed a few pubic hairs in my underwear. It has never happened before, Is that normal?

Absolutely. All of us are losing hair of all kinds, at all ages. Most of the hair shafts that are lost are replaced by growth of a new hair shaft from the same follicle. In some areas, such as the scalp, hair loss can be permanent (alopecia) in both men and less commonly, in women. In the pubic region, however, hair loss is almost exclusively replaced throughout life in both sexes.
Normal. We are losing individual hairs all of the time it is a very normal process.