.....PLEASE ANSWER

Is it possible for EVERY brand pregnancy test to be negative but you still end up pregnant?? Lol, I took clear blue (digital and regular) I took about 5 EPT’s and I took like 3 first response, I went to the doctor for blood pregnancy test and ot was negative...All of those were taken 2-5 months after sex. My periods are irregular. Any help?? Should I definitely stop worrying? The blood test was taken 5 months after the sex. Negative.