Im Scared!!!!!

Bookah
Hello everyone im currently 6 weeks and 3 days.. I have been in the hospital 3x in the last 2 weeks thats ive known that im pregnant. I was having some bleeding and cramping at first. It lasted 6 days exactly. Then today leaving out the house for my WIC appointment, I all of a sudden had cramps so bad that i couldnt walk! I went to the hospital and they said my hcg levels should be at least 8000 9000, but my levels are only 4000... They also said they could not see anything in my uterus... Please help me has anybody else experienced this? Idk what to do... They are monitering my levels every 2 days now..