Could i be?

My bf and I had sex, kinda unprotected (withdrawl) on the 24th and 25th, my period was due on the 26th. This might be navie of me but i didnt think you could become pregnant that close to your period. I’m late now, not too late, but i am a little worried, because i havent gotten the normal signs that my period is coming, which i get everyy month without fail. I’m most likely freaking out for no reason. Buut i would like to know what you guys think. Do i have reason to worry?