Please take the following advice with a “grain of salt.” I am not a priest and I am not an expert of any kind. That said:
I’m not convinced that anyone other than you and your confessor can determine whether or not you have committed a mortal sin.
As you probably know, three conditions are necessary:
- Serious matter
- Sufficient reflection
- Sufficient freedom
I will not offer a judgment, but if you feel guilty then you should at least make an act of contrition and plan to confess this sin at some point. Do you attend confession regularly? If so, this incident is the kind of thing you might remember to confess. If you don’t attend regularly, why not?
Some questions to ask yourself in determining if the sin was mortal or not:
Could I have reasonably avoided this?
Did I seriously injure someone else or myself physically or spiritually or emotionally?
Did I know at the time that what I did what seriously wrong, but I just didn’t care?
Did I purposely choose to do it, or did it just “happen” without thinking about it?
Was I in an intense emotional state at the time (anger, rage, insanity, depression, etc)?
Is this a habit that I cannot seem to break no matter how hard I try?
Did I relish in what I did, knowing it was “wrong” but not caring?
You answers to these questions may help you determine whether a sin is mortal or not.
However, all sin is bad anyway. Worrying about whether a sin is mortal or not will not help you significantly. If it isn’t too inconvenient, why not go to confession? Please don’t misunderstand, I am not encouraging you to become scrupulous and lead a life of anxiety which drives you to confession everyday. I am just suggesting that you try to remember the sinful things that you do, ask God for forgiveness and grace to avoid them, and trust in his mercy in the sacrament of reconciliation on a regular basis. How “regular” is something for you and your confessor to determine (in my opinion).
Don’t worry friend!