Hi Doctor, I Hope Are Doing Well ! I Am

Hi doctor,
I hope are doing well ! I am here for help. I am 29 year old. Mother of two kids ( 9 year and 5 years old ). I was done PPS 4 and half years ago with a laproscopic surgery. But now I missed my periods. LMP was 23/8/2016. I have checked test at home it shows positive with a faint one line. So I went to hospital and they also tested to confirm. That also positive. I have gone through 4 scanning till yesterday but doctor cannot find any possibility in my uterus. And also checked beta HCG . Monday HCG shows 490 MIU and Wednesday test shows 856 MIU . Doctor said me to scan again on Saturday. I don't know what is going on. So confused and depressed. Can you help me to know what it is. Is this an ectopic pregnancy? I don't have any pain till today.