Implantation?

My boyfriend and I had unprotected sex on the 21st and 23rd of this month. Tonight I had mild cramps and back pains for about 10 minutes and now I'm just experiencing some nausea and stomach aches. My period isn't due until October 16th (I have long cycles) and was wondering if it could be implantation cramping? I am currently ovulating right now. Is there any way possible? I've read where people can feel symptoms this soon and I don't want to seem crazy 😅 please help