Mirena help/concern

Hey I’m a little concerned about what’s going on with me. I had my mirena places at my 6 week postpartum check up and all was good. I never had a period or any spotting. My husband was deployed for 6 months shortly after so I was not having sex. He recently came home, I resumed sexual intercorse and have been bleeding/spitting for the past 3 weeks. I took a pregnancy test because I was worried about having an ectopic pregnancy (I’ve had before) test was negative. Anyone know what could be going on?