Very confused and scared

I found out I was pregnant at exactly 4 weeks. at 5 weeks and 1 day I had some brown spotting and over the next few days I had red bleeding and spotting. At 5 weeks 4 days I had a hcg blood test and the level was only 86. They repeated the test 2 days later and it had dropped to 33. The following day I started bleeding quite heavily with clots and gradually got less until it stopped after a week. I was told to take a hpt after a week to confirm it was negative, which it wasn't. Yesterday I started bleeding again and today, at what would have been 8 weeks 2 days, I had a scan because I am still getting positive hpt results. There was nothing showing on the scan and I was told everything looked normal but they decided to do another blood test just to be sure. My hcg levels have increased to 97!! I now have to have the test repeated again in two days time. I really don't understand what is going on and I'm really scared that it may be ectopic. Has anyone else experienced anything like this?