Whats going on with my period!?

So last month and this month I'd been two days late on my period, but when I get it I rarely have any symptoms like I did before until the day I get it for example lower back aches and cramps. My period is a dark brown at first and then when I wipe its red but it only last two days and I don't even have to wear a pad because its not heavy at all..!? To me this is weird it never happened before...What can it be ?