What Causes Extreme Cramps In Lower Stomach And Vomiting During Periods?

I started my period on wed (two days late) which is normal for me, but then about 4:00 am thursday morning i woke up to the worst cramps of my life. They were in my lower stomach- when i got up to get midol i almost blacked out. Then the pain was so bad it made me want to faint and throw up at same time. Then my body was freezing and shivering so bad- is it possible to miscarrie even if i didnt know i was pregnant and if so will a dr be able to tell even 2 days later