If you meditate deeply on the passion of Christ, and start to shed tears because YOU/I are the person who caused His suffering, because we offended Him, you can be sure you just experienced a Perfect Act of Contrition.
Also kiss the Pardon Crucifix, and make sure it is properly blessed. If you don't have a Pardon Crucifix get one, but don't forget the blessing, Pardon Crucifix has a special blessing.
None of the above take the place of Confession, so get there as soon as possible.
God does provide.