What Causes Mucous Filled Blood Discharge During Periods?

my bf and i tried to have sex. it was my first time, it hurt me so he pulled out with out having ejaculation. 2 days after i miss my period he i started bleed. it was kinda mucusy and more blood than usual blood i bleed.i also had cramps which i never got before. my friend said i probably had a miscarriage. is it true?