Anything is possible when you have been having unprotected sex.
So are you saying I could be pregnant?
Can you fall pregnant having sex 4 days before ovulation -- yes. Sperm can live that long in your system.
Feeling light twinges in your side is that ovulation -- could be from ovulation, and either would be ovulation itself or the flow of fluid into the cavity left behind by the egg after it ovulates.
I wouldn't use this as a method of birth control. By the time you feel the twinges, ovulation might already have come and the egg is sitting around waiting for the sperm.