Spotting instead of flow during period time
Spotting at the time you should have your period could be several things.
First, you might just be having an 'off' period. Hormones get mixed up with stress, change in diet, new exercise routines, even being around other women with whom your cycle is beginning to sync could cause a wonky period.
It might just be the beginning of your period, because many women spot before their full flow begins. Just because it may have never happened to you before doesn't mean that your cycle isn't changing. I didn't used to spot before periods, it always started heavy and in a swift minute... But nowadays, I spot almost invariably beforehand.
If you're later in life (and surprisingly, this happens to some young women also) it could be the onset of pre-menopause. Cycles do change throughout the course of life.
One thing to consider, though, is pregnancy. While it's not likely you're pregnant if you're spotting during the time of your period, it is absolutely possible. Some women even get what appear to be full blow periods during pregnancy and don't find out until later! You may have ovulated later in your cycle than normal or just ovulate late normally, and the spotting you're seeing could be implantation.
Usually implantation bleeding occurs about a week before your period should begin but it does vary. Sometimes it's a little bit of blood, sometimes it looks like a period. It could be pink, red, or brown. It all varies so much from woman to woman.
If you're spotting at the time you'd normally have your period, I'd pick up a dollar store test and check for pregnancy, just in case.
Can you ladies think of other reasons you might spot during the time you'd normally have your period?