Pressure

Hey ladies!  I was curious if anyone here has experienced pressure in lower abdomen before finding out they were pregnant.  For the last few days, anytime I lay on my back I feel pressure in my lower abdomen. I took a test today but it was negative.  I'm supposed to start my period in 5 days. I have been feeling very 'off' the last week or so. Just not my normal self.  So I was just curious if anyone has experienced this pressure before finding out you were pregnant.