Hi I Miscarried About 6 Weeks Ago It Was A

Hi I miscarried about 6 weeks ago it was a natural miscarriage and my doctor confirmed everything was gone I went for a check up last week and my urine showed I was still pregnant so they had me take some blood work for beta testing I went today and they said it was 355 so they took more blood to test and I have to go back in a week to see if it decreases. I had admitted to having sex twice since the miscarriage and I got what I thought was my period on June first since I had stopped bleeding for a month after the miscarriage but I only spotted for about 2 to 3 days is there any reason to be concerned