Just in my head?

Hey guys, so I had unprotected sex where he came in me on Sunday. I’ve been on the pill for 3 weeks and I took plan b as soon as I got home within an hour. Is it too soon to feel anything? Or could my breasts hurt and nausea from plan b? Or am I just in my head..my period on my sugar pills should be due in 2/3 days... when can I accurately test