Ok so I have had mirena since like July of 2008 and my fiancé and I no longer worried about having another kid so close to the one I had in June but now all of the sudden I have a belly. I woke up the other morning and I have a belly out of nowhere. I don't think it is normal weight gain because it is only my belly I am actually losing weight everywhere else... like from a size 5 to a size 3 to 1 so we took a pregnancy test several times and all of them are negative. Is it possible to get pregnant on mirena and not know and when you test it shows negative every time?

Oh and I still have my period normal and all kind of... I had it normal this last time stopped for almost a week then spotted for a day

It's possible, but since you had a period as usual, odds are you aren't. By the time you would be having a belly, you would most likely have had other symptoms as well.

See what happens when your next period is due. If you have other possible symptoms, you can always see your doctor about having a test done there and having the IUD checked.