Having pregnancy symptoms but on the pill... Am I pregnant?

Okay so I had unprotected sex with my SO 3 days before I was supposed to start my period. I started , it lasted about 4 days. But now it's been 12 days since possible conception & im having cramps , hot flashes , shortness of breath , headache , fatigue , etc. I took a cheap pregnancy test today & it came back negative .. Could it be too early for the test to detect or am I overthinking ??