4 days of light brown, an hour of pink and back to brown again

My periods are always heavy and dark red for a week each month, the first day i get brown and the rest is thick dark red. Im a little concerned this month as i have had 4 days of light brown spotting, 1 hour of dark pink (barely covered a pad) back to brown again today. Im on the iud but i dont use condoms ... should i be concerned as my periods never been like this