Yikes! I am so sorry to read about your experience with the friend's father who was in an adult film. That just has major yuck written all over it. I am so glad you are okay.

As far as your feelings for your ex goes, and the anger you have at her current girlfriend, it seems to me that this is natural, and as much as I would like to wave a magic wand, and make the pain go away, I cannot. Trust me, I wish I could, because I know how hard it is. Especially when you have to go to school with them and see them interacting every day, and you are friends with her new gal. That is tough.

I guess my only advice, is that it is okay to allow yourself to withdraw from these two for awhile this year. If you want to give yourself a chance to heal, you have to choose to walk through a new door, and allow a new chapter in your life to begin. This is a choice that only you can make.

For example, you could try to get alot of classes with your ex, or join the same clubs or sports teams (if you guys do that) and make an effort to be "around and available".

OR, you could own your power and set your own path.

This would mean doing something new, like joining a group she is not a part of.
It could mean joining the drama club or starting a new sport. That is scary and
uncomfortable, but getting out of your comfort zone always is.

Or try and take classes that she is not in, so that even if you have to see her and her
new gal in half your classes each day, the other half a day you get a breather.

Don't hang out with her and her ex after school, if you then just go home and mope.
I know how extremely difficult this is when you are in school together.
You may not have alot of options. But, those that you do, make use of.

In this way you can take care of your own emotional needs
and give yourself a chance to heal.