Skyla failure

I've had skyla in for almost two months and I've had the worst cramping I've ever had in my life! It went away for a while, but now it's back. Also I have been extremely tired, nauseous, have had pain where implantation is "supposed" to be, and my breasts are big and very sore. These are all pregnancy symptoms. But I have Skyla. So how accurate is Skyla really? Thanks so much! Also I will take a test today, JUST to rule out pregnancy.

Update: also light spotting when I wipe. It's kinda jelly like too.

Update #2: tests were negative. So what's up?