hcg not doubling


hi guys I'm abt 4 weeks and Friday I started spotting I went to er they checked for tubel it wasn't thank God but I do have a ovarian cyst uti and they did my hcg it was 344 went to the Dr today still spotying and light cramping they did hcg and it was 475 it's going up but it is not doubling I'm on bed rest til they do another test Wednesday anyone been through this I'm scared for miscarriage prayers please