Irregular periods

Hi girls am 17 and ive been having irregular periods lately, ive been on for 4 days then off for 5 days then back on and my blood is not normal sometimes its brown through out the whole period and then sometimes its dark red. I had a time when i was 14 where i was on a heavy period for about 2 months none stop but now am not having normal periods again but this time its less blood and I’m on a fee times a month and its just so strange. Has anyone ever had this before?