hcg??

hi everyone I had a miscarriage last month August 26 on August 20 doctors checked my hcg level and it was at 118 they had me come back 2 days later and tested again and they dropped to 71 so I then miscarried. I recently took a pregnancy test and it came out positive I called my doctor because I was curious and they had me come in to draw blood due to the fact it's almost been a month so the result came back 31 and they had me come back in 2 days and I got called today that my levels rised to 90 can this be a new pregnancy and are those numbers good i think I'm only about 3 weeks if I am pregnant I have to go back in a week to draw blood??