I had protected sex on 20th march. i got my periods 2 days late on 8th april, and it is lighter than usual. could i be pregnant or is this normal?

Below: Wait ten days and do a HPT, if it is positive, you are PG. Doubt it will be positive. This may be a normal variation of your menses.

Check a test: Since you had your period it is not likely that you are pregnant. If you think you might be pregnant check then check a home pregnancy test. They are cheap, reliable and available at any pharmacy. This is the way to confirm.