as you missed your periods on July, you might have gone for pregnancy
test at that time.
the spotting you had in august could be that usually seen in early pregnancy or that is hypomenorrhea
means scanty flow during periods,
so you better consult gynecologist and go for blood test
for pregnancy which will rule out the possibility,
when you are very much desirous of pregnancy you can have symptoms of pregnancy even in its absence it is called spurious pregnancy,
so if pregnancy test comes negative you can go for ultrasound
which will possibly find out the cause for menstrual irregularity and also confirm absence of pregnancy.