please help. tmi post.. miscarriage or??

My son just turned 5 months old and since receiving my period again I've been getting it twice a month so everything is irregular I feel. I haven't gotten birth control and have been having sex. I've had sex quite regularly but the last days I charted were the 18th/19th. Could I have been possibly pregnant from those days? On the 25th I was cramping like I was before I found out I was pregnant with my son. I thought I started my period yesterday but then it got heavy instantly. I'm soaking through my pants within 20 minutes with a super tampon. I've passed 3 large clots, one tennis ball size, and two golf ball size. I'm not cramping like I usually do but I'm bleeding very heavily...?!