IS IT POSSIBLE TO STILL B PRGNANT AFTER 4 NEGATIVE TST?

I GOT WHAT I THINK WAS MY . EVEN THOUGH IT WAS LATE IT CAME ON THE LAST DAY OF THE MONTH WHICH WAS MARCH 31 AN ENED APRIL 4. I HAD ALL THE PREG SYMP. BLOATING,TENDER B, THT ALWAYS FULL FELLING, ETC. HAS ANYONE HAD THAT HAPPEN B4