A week ago i experienced really bad stomach cramps in which i could not move, the feeling in my stomach was as if knives were cutting me, i never experience any kind of pain in my stomach when my period is about to show. 

During this episode of severe stomach cramps, i began vomiting, i vomited at least 5 times and then i forced myself to sleep.

Yesterday i started to experience cramping in the area of my uterus (which is abnormal for me as i never cramp in this area during the time of my period), and today i got my period? Im sorry to sound gory, but when i went to the bathroom this morning there was a large blood clot about 2-3cm in diatmeter. I went to the bathroom not long ago and there was a string of blood about 4 cm. 

Just for some background info, i had unprotected sex with my boyfriend about a month ago, so i am not sure if i am experiencing a miscarriage? i havnt been experiencing period pains, the only pain i have had was from the bad tummy cramps last week.

your comments would be greatly appreciated.