What Causes Cramps And Vaginal Bleeding During Pregnancy?

hello my name is tabitha and i found out i was pregnant about 2 weeks ago i went to the doctors and they said i was about 6 weeks. about a week later i had sever cramping and moderate bleeding i went to the doctors they then checked my cervix and said it was still closed so that was good and they sent me for a sonogram. the sonogram showed a sac and a yolk sac but no baby and the tech said i was measuring at 5 weeks and to come back in a week for another one. i have my sonogram tomorrow but i am worried because i had a test done to test my levels the first day were 345 then the second day they were 331 is this normal?