If you are worried that you might be pregnant the best thing to do is buy a test to find out. You have gone past the date your period was due (you say you had a light one) and so a test will be very accurate now:
I have a link to some very inexpensive pregnancy tests on my hub: https://kindredbond.com/having-baby/how_to_know_pr
I think they cost $2.73 for 10.
Put your mind at rest by doing a test, otherwise you will be worrying for the next month wondering if your next period will come or not.