according to your description the possible causes for your delayed periods are,
-as you are 45 now, these symptoms means delayed periods, night sweats
and others could be because of perimenopausal phase, indicating hormonal
imbalance and nearing menopause
normally women can attain menopause around 50 years, but in some people it can occur around 45 also.
-other cause could be pregnancy
as your are thinking,
but normally urine pregnancy test kits can identify pregnancy after missed period,
now you repeat the test, if that is positive it is ok, if not consult gynecologist and take opinion.