PLEASE HELP

Hey ladys

Im needing so advice or wondering if anyone has experienced this.. on the 6th of may i went and got bloods done.. monday 11th went to doctors to get results pregnancy test came back at 6hcg so needed to have an urgent blood test so see if it had risen that night got a phone call from doc to say they are now 50hcg so im pregnant then went and had my bloods done again the 15th and they had fallen to 20hcg.. does this mean i am no longer pregnant. Or could they rise again and the pregnancy be fine? I need some advice please