Advice please!

I had a missed miscarriage on July 12th. I was supposed to be 9 weeks, but my little one passed at 8 weeks. I had to have surgery on the 16th and my husband and I were told we could start trying again once I stopped bleeding. I spotted and then 2 weeks later had heavy brown bleeding. Like the doctor suggested, I took a pregnancy test Monday and it was negative. I took another today and it was positive. Could I be pregnant? Should I cal my doctor? Thank you for the help! I’m so nervous and don’t want to get my hopes up!