HELP! HUGE UNUSUAL BLOOD CLOT

i was 4 days late for my period and then woke up with really bad cramps. Later on in the day I started bleeding but it was only small blood clots coming out. All day i felt a lot of pressure down there so went to the bathroom and this came out. I’ve never experienced this before and can’t find out what the white spots are. Has anyone experienced this before? today is day 2 of my period and it is very light, hardly anything and no cramps or pain. Please help.