Could i be pregnant on the copper coil?

 i am very confused and i dont know what to do next. i have been on the coil for 3 years and i have NEVER missed a period. May my period was very light and june was none existant, its now coming round to my next date and nothing is happening again i have had back pain, tender boobs and twinges in my stomack. home pregnancy tests are telling me im not pregnant so im scared to go to my gp incase they will think all of this is in my head.