Advice please!

According to Ovia im supposed to start my period today, according to Glow its tomorrow. This afternoon I had bright pink spotting when I whiped,  now 4 hours later nothing has come out but when I wipe it's brown.  Typically with my period its immediately drops of blood in the toilet (tmi sorry). Anyone experience this?  I took a test 2 days ago and it was negative.  I've also had slight cramping all day long.