menstrual cycles can fluctuate due to many factors,
like stress and strain, weight gain or loss, any recent illness etc can affect the hormonal
balance at different levels of hypothalamo pituitary ovarian axis and can lead to menstrual irregularities.
as 30th May falls on fertile period there is chance of pregnancy
in that case your bleeding should be implantation
now you better consult local gynecologist and undergo blood test
for pregnancy which will rule out the chance of pregnancy.