What Causes Heavy Bleeding And Pain During Menstruation?

hi. i was supost to come on my period on the 29.12.10 but i came on xmas day. but this periood isnt like my normal ones. ive had heavy bleeding, clotting and pain down my right side, my husband and i have been trying for baby number 2 and whilst trying for my 1st child i had a miscarriage just before i fell pregnant. my periods are very regular and never early or late. do you think this could be another miscarriage?