Lower back cramps

So my period started 31st but it was a weird one it was a medium flow for about 2/3 days then it just got super light and my tampons were coming out white and spots of blood my period only last 4-5 days max but now it is the 3 and my lower back is cramping and I’m spotting again but the pills (Midol) aren’t working. Anyone have any idea what might be going on ?