Best is to rule out with a Urine pregnancy
kit. Anyways it appears that your cycles are regular but the volume of bleeding is very less indicating oligomenorrhoea. There are various causes of this condition including stress
to problems in the uterine wall. I suggest you wait it out for the next cycle and if you still have the problem, you may visit your Gynaecologist who will be able to examine you and advise a proper line of management.