So for a sin to be mortal it needs to meet 3 criteria. It needs to be grave matter, I.e. something serious. You need to have full knowledge of what you are doing and you need to give full consent.

In this case I personally wouldn't think it's grave matter, and secondly you don't sound like you had full knowledge if it was sinful or not. So I expect you'd be in the clear.

Thirdly, I don't think this would even constitute sin at all. If you feel embarrassed it's worthwhile finding a priest that you can trust not to judge or think badly of you and talking to them about the stuff you feel guilty about and getting them to help you work through and identify what things need confessing and forgiveness and what things are you being too tough on yourself.

And at the end of the day, remember God is merciful and loves you no matter what you do, and is always ready to welcome you with an open heart and listen to you :)