Cramps and spotting 1-3 days after sex

Is it possible to conceive already !? Had sex on 4/24 (trying for a baby) I spotted a tiny bit right after sex and the next day when wiping and I have almost period like cramps today (no spotting) with nausea feeling in my gut and a headache. My ovulation day isn't supposed to be til this sat (but maybe it's "off' this whole week is supposedly my high fertility week) my days may be off

And my period is not due til may 13? So weird.