Concerned- Sorry this is long

I was on the Nexplanon implant for birth control. My husband and I decided to try for baby number 2, so I had it removed March 20. I had some very slight off and on spotting April 1-5. I did not consider this a period, though my ob/gyn declared it one later on. April 22 I got the faintest positive pregnancy test, went in for blood work and it came back as a 0. I continued testing at home, and they kept getting darker. I called my doctors office again, they obliged by sending me for more blood work basically to shut me up, as no one there thought I was pregnant. The blood test came back with an hcg level of 15. They sent me back two days later for more blood work which came back with an hcg level of 105. They officially considered me pregnant. I have a history of ectopic pregnancies so they send me for ultrasound early. I went for my ultrasound today, and the tech said she didn’t see anything. There was nothing in the uterus or in my tube. For now they are saying they can’t rule out ectopic, miscarriage, or a healthy pregnancy as I may not be as far along as my ob and I thought. I have been having some spotting/light bleeding for the past 36 hours, but it has mostly stopped and turned brown. I went for more blood work this afternoon which I will get the results of tomorrow, hopefully. I am also supposed to go back Wednesday for repeat blood work. Has anyone had anything like this happen to them? I am worried I either have another ectopic or I have lost the pregnancy.