Thanks for posting your query.
6days is good enough time to detect pregnancy
, still negative test is also a possibility so please repeat the test after 7days.
Your symptoms may be of early pregnancy but lower backache
and frequency of urination can be indicator of a urinary tract infection
if you are willing to be pregnant eagerly then it may be due to you psychological stress
This phenomenon is called pseudocyesis.
I hope your query has been answered.