I am finally bleeding on day 48 of my cycle. my last period came on day 39. why does my cycle keep getting longer am i pregnant?

Maybe not: A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If she resumes her normal regular periods, then she is not pregnant, and a test is not needed.