What Causes Pregnancy Symptoms While Having The Contraceptive Coil In Place?

Hi. I have had the contraceptive coil in place since Augpust 2015, but for the past few weeks I've been noticing quite a lot of pregnancy symptoms, more than would normally occur with contraceptives. No vomiting but heavy nausea which seems to have gone, heartburn, lasted for a few days about a month ago however this week I have had it every morning and then it hopefully leaves again after a few hours. I've also had extremely tender breasts which have become very veiny, been bloated for over a month and a month ago I had the worst fatigue I've ever experienced for about four-five weeks, and now I am back to my normal insomnia. I took two home pregnancy tests around two-three weeks ago, five days apart and they were both negative. However, my mother tested negative until she was thirteen weeks pregnant. I have also developed a very light brown small line on the bottom of my abdomen (I'm very pale skinned) and I've been having two-three intense tension headaches a week for the past two months too. I have a doctors appointment tomorrow. I've also noticed that my coil feels different, like it is lower down than it used to be. Any advice or opinion would be appreciated. Thank you.