Could Abdominal Cramps, Nausea And Discolored Menstrual Bleeding Be Sign Of Miscarriage?

hi doctor
i am 30 year old, we are trying to conceive off and on. but i had very severe cramps just before my period and it was one day late. but i had it so bad i was feeling better while sitting on the toilet but nothing came, felt so nauseated as well. cramps were in lower back, lower abdomen and slowly went to mid abdomen. my period was also not normal this time, the colour of the blood was also not normal as i used to have before, i am really worried, could it be a miscarriage, i never did the pregnancy test because it was just one day late. And i had same situation in feb 2011 as well. Normally i don't have any pain during periods, i am very regular as well just +- one -two days. please help