Is it normal to bleed 4 days before period?

The app says that my af is due in 4 days. My cycle usually lasts for 29-31 days. I'm currently on CD 28. Earlier I went to the bathroom to do my business and I noticed that the toilet was pretty dark. When I flushed the toilet there was a hint of redness in the water, as if it was mixed with blood. I checked my cm and there was definitely blood in it. It's weird because this is the earliest my af had arrived. I haven't had sex since September or October last year and the last time I had done something sexual was when my boyfriend fingered me on November, but I've already had my period on December. This is confusing me because I'm used to having my periods at a later time 😥