Low hcg goes down then up but told notviable?

Im hoping by sharing I can get some support. So sept 4 got my first bfp the first month we decided to stop trying:) my happiness turned into determination to get the earliest appointment since i have a history of low progesterone and was using cream in the meantime. That Thursday hcg was at 42 pg 2.5!. I immediately was prescribed 400mg and started Friday. The obgyn finally saw me Monday found hcg @ 32. Obgyn redid test 48 hours later with a hcg at 44 pg at 17.5. Those few days were a roller coaster (still is). That same day they did an ultrasound due to sharp pains and tech could only said "no good news or bad news" since nothing was seen which to me would confirm I am not 6 weeks(is that right?) They called with results and was told "its weird they went down then up again. but because it didnt double, to stop the progeterone and prepare for a miscarriage."

I know I am not as far along in the pregnancy then they think cause i ovulated late. But they say it still not viable. What do you think?