What counts as going to confession ASAP? Does that mean calling up the church after you’ve committed a mortal sin, or going at the next scheduled time (you can make) which usually is the next day?
It means going As Soon As Possible.
If, on the day you commit the sin, it is possible to get to confession, then go.
Some priests may be able to help you if you catch one before or after Mass, some may not- it all depends on what they have planned.
Best advice- don’t sin!!