My lmp was 9/20 and ended the 24th I had sex the 20th at midnight my boyfriend came in me and my period later came that day in the afternoon then again he came in me on the 24th. Today I'm experiencing sore breast I'm kind of feeling nausea. My stomach feels weird and when I lay on it or on my back I feel my stomach tightening. Maybe I'm being paranoid I always thought your periods would be your safe days.
Your sexual intercourse on the 24th could have gotten you pregnant, although it's unlikely. You're right, typically that would be a "safe day". You can test when your next period is due to be sure.