I got ectopic pregnancy last year and also performed the blood test to check. According to my doctor, if HCG level for 1st July is 800, the HCG level should be raised to 1600 on 3rd July for normal pregnancy case.
Actually, I faced 4 times misscarriage before and have a 2.5 years old daughter. I'm also in week 4 pregnancy now but have bleeding a few days ago. My doctor asked me to check 2 weeks later. For I've more chance to get the ectopic pregnancy again. I can do nothing but only waiting and praying. I can understand your feeling.
Please follow to doctor's advice and perform blood test again. God bless you!