12 days late with mirena.

I've have mirena for over a year now and my periods have gotten much lighter. I completely skipped my last period and I'm now 12 days late. I took a home pregnancy test and it was negative, but I'm not sure if it was a false negative. honestly, I'm at a place in my life where if I get pregnant I get pregnant. I love my bf and I'm happy to have his baby. I'm more nervous about his reaction, since it isn't really anything we've discussed at all.