My period came 18 days late....at least I think it’s my period.!!

Hiya...my period was 18 days late and I was pretty sure I was pregnant but hoping it was just a scare as I had two negative pregnancy tests. For the past couple of days I’ve had a slight tint of red in my fluids down there...I’ve just been to the toilet and I have normal blood in my area as if it were a period. Should this be something to worry about? Please help!