I started my period, but later I got terrible cramps

I am on depo provera and I have been on it since the beginning of January. My boyfriend and I had sex 2 weeks ago, and 3 days ago I started my period but it was just normal beginning bleeding when I first started but the second day I had terrible cramps and I couldnt even get out of bed, today it was the same except they were really bad and they feel like what I think are mild contractions. I went to go and change my feminine product and I saw that there was a thick creamy colored thing that looked like a line and then there was a little red thing along with blood inside of a little sack of this thick stuff. And It looked like it could have been an embryo. I need to know if this was a miscarriage.