Birth control and problems

Had anyone ever gotten pregnant with the iud mirena? I've had it for almost 5 years, I'm due to have it taken out in November, but lately my breasts have been very tender, my back had been sore (upper back not lower) and I seem to be gaining weight for no reason. But when I take a pregnancy test it comes back negative...I'm confused and don't know what to do or think. Any advice or experiences similar would help. Thanks in advance!