Thank you for your query.
Any kind of altered menstrual bleeding always raises the chance of pregnancy
I would advise you to go for a home pregnancy test after 3 - 4 days if your period doesnt show up by then properly.
Other causes of such altered menstrual bleeding could be :
Stress, anxiety, emotional upheavals, frequent travelling, intake of hormonal
disorders, polycystic ovaries
Such scant spotting once in a while is a normal occurence also.
To reassure yourself completely, you can visit a gynecologist for detailed evaluation and tests.