Positive hpt after miscarriage

Patient: My husband and I conceived our first baby in Aug. then sadly I miscarried it only Aug. 28 (I was 4 weeks 6 days pregnant). I had brown discharge for 2 weeks so I called my doctor and they had me come in and ran 2 ultrasounds and saw no tissue and did a hcg blood test (level was 178). Then 3 days later they had me come in for another draw, level was 240. So then they had me do another ultra sound to make sure there was not an etopic preg. still in there and they saw NOTHING. So then 3 days later another hcg test and it was 220. They said I was very fertile and my levels will drop and to go home and not worry. So here I am (6 weeks post mc) and my breasts are tender, muscles in stomach are sore, and NO period since mc. Took 3 pregnancy tests and all came back POSITIVE! So what are your thoughts? I don’t have the money to go back in and have them run all those ultrasounds and such for nothing if it is nothing. Is there any way that I could still have hcg hormones in my body high enough for make hpt positve 6 weeks after a 4wk6day miscarriage? I have read so many different opinions. Thanks!