Lately my fiancé and I have been having quite a bit of (unprotected) sex, and the other day I started getting these deep cramps that only last a few seconds and then go away. They're not sharp, just aches, but hey hurt slightly more than my period cramps. My fertile window started two days ago, but we haven't had sex during it yet. I was wondering if anyone has had any implantation cramps, and if you could tell if they were different from period cramps?