low hcg level :(

I should be 4 weeks. I have missed my period and have had a lot of positive tests. I was feeling terrible with painful cramps. so I went to the hospital.I have never found out I was pregnant this early always between 6 and 12 weeks. so they gave me an ultra sound we all know Nothing shows until 5-6 weeks. defiantly nothing there. doctor tells me my hcg level was only 22. I'm used to hearing thousands so I was freaked. he said you're having a miscarrihaving a tuble pregnancy witch I was suspecting from the pain. I go home and the next day get a call from a nurse at my doctors office to tell me I need to come in the am to do a repeat test because if I ovulated a little later 22 can still be a regular hcg level. she said normal for 3 weeks is 5-50. so we will see tomorrow but my gut is telling me something isn't right.