Having a very light cycle.

I have a very normal very heavy cycle for all 4 days. I'm on day 1 -6/15 and had unprotected may 20th which is the last day of my cycle and the day before my period. I have a 24/25 day cycle. I think i had a normal period the entire 4 days the previous month, but this cycle I'm soo light. I didn't even consider pregnancy until a few days ago when a few different people have brought up how moody I have been. Is it possible for me to even become pregnant the day before or night of my period and still get an irregular light period during my cycle? Thanks