In that case, it is not at all true that either all 4 will get fertilized or none.
4 eggs might have been released due to the medications given to induce ovulation, however the egg quality is not uniform.
Either 1, 2 , 3 or all 4 may get fertilized, there is no way to predict.
Only rarely will all 4 get fertilized and implant.
Even if more than one get fertilized, implantation
of more than 1 eggs is rare, so dont worry.
If an egg does not get fertilized, it is naturally absorbed by the body and destroyed , it will not produce any side effects.
So remain stress
free and sexually active.
All the best.