Currently I am 15 days late for my period, which isn't uncommon, I think the most I have gone is 19 days, but the strange thing is for the past two weeks my boobs have been so sore. Usually my boobs get super tender around my period and I think since it has been going on for so long it is hurting more than usual. I already emailed my doctor about it to get her opinion, but I don't know why I am stressing. I keep telling myself I am not pregnant because I have an IUD that's 99.9% effective and I only had sex without a condom once the whole month (I use condoms as a backup), so my chances are very unlikely.

Anything you can say to calm the nerves? Or any similar experiences? 

Is my body just not reacting well with the hormones in the IUD? 

Thank you!