sudden short period of 2-3 days , is it normal ?

I have been skipping lunch for a month now . and i have also been slightly worried of being pregnant through fingering .
recently , just this month , my normal periods of 5 days became as short as 2-3 days. I usually have painful cramps but this month, the cramps were bearable . my periods were normal , and not heavy as it usually would be on the first day.
May i know if this is normal ? what can caused my periods to be shortened? and what can i do to make sure everything goes back to normal ? please reply soon ! thank you !