postpartum period

I am on my second cycle since having my daughter 18 weeks ago. I noticed during the blood kind of a foul odor, just like the bleeding right after baby but not as strong. Last cycle I called the doctor and they had me take a pregnancy test and it was negative, asked if I potentially forgot about a tampon, if I had a condom stuck in my vagina, etc. They didn't seem very concerned after saying no to all of that. I'm just wondering if anyone else has experienced this?