HI, thanks for using healthcare magic
Oligomenorrhea is the terms used when there is a delay in periods of greater than 35 days.
At your present age the most likely cause is
menopause which would result in irregularity in periods.
Pregnancy tests detect the HCG hormone, this hormone can usually be detected in the urine 12 to 14 days after conception. It should have been reading positive at time you tested it but you can consider repeating at this time to ensure that pregnancy is not the cause of the delay.
The other causes of oligomenorrhea are: (1) high
prolactin levels- this is a hormone secreted in the brain
(2) high levels of thyroid hormone
(3)inadequate diet
(4)stress either physical or emotional
(5)PCOS- this stands for
polycystic ovarian syndrome but is unlikely to be diagnosed at this stage
If the repeat test is negative, you can consider visiting your doctor who can do blood tests to see if menopause has started.
I hope this helps