period or not?

hello! so I was swimming earlier and when I came inside as I was taking of my swimsuit I noticed a little blood so I went to go wipe and there was more blood. according to this app, I should start my period for 1-2 more weeks and I haven't experienced any symptoms of starting my period. what could this be? I have been wearing tampons since earlier but should I be? I am not sure what this is but I'm slightly nervous about it, any thoughts?