All the things you mentioned are sins and should be confessed; there isn't any one that I would say is a mortal sin because frankly I don't think you are mature enough in some of these areas.
Tell the priest everything. Although you may feel embarrassed, he has heard it all before so don't worry about that.
You only get one life, and one shot at your youth. Stop wasting it; there is no excuse for not doing your best. Boredom and a lack of interest don't cut it. God is counting on you to become the best version of yourself, so do it. Even if you don't see how certain studies really apply to your interests, do your best anyway. The habits you learn in doing, will forge your character.
Think about this:
- Do you want to get married someday?
- Have a family?
- What kind of a husband do you want?
- Do you want him to be a second-rate version of himself?
- Someone who doesn't try hard?
- Do you think your ideal man wants a wife that doesn't work hard?
I know it is hard for young people to imagine their distant future, but your decisions now affect that. Figure out whatever is in your way to getting on that path, and move it out of the way.
Then you will have a lot less to confess.