Pressure after orgasm?

I was bad this month and didn't use OPKs because I didn't want to get too stressed so I'm going to guess that I'm anywhere from 8 to 11 dpo. For the last two nights when I had orgasms I've had almost period like pressure afterwards that goes away within minutes. I've never had this before any period ever. Should I be hopeful or is this just a sign of my period coming? If I'm 11dpo I'll start in 3 days and if I'm 8dpo I'll start in 6 days.