What Are The Symptoms Of Potential Miscarriage?

I was a month late for my period. I started having these constant muscle spasms in my lower abdomen for two days. After that I started bleeding and went through a super tampon within an hour and also had cramps. I usually have light periods with no cramps that only last a few days. I am now on day six of bleeding, but it isn't very bad anymore. Could I have had a miscarriage? Should I go see my doctor?