Thank you for reaching out to the Trevor Project; that is extremely brave and mature of you. Anytime you need to talk; please feel free to contact us. We are available 24/7.
Growing up in this day and age is difficult. There is no excuse for it; bullying someone is a terrible thing to do; and to endure. And it's an awful thing to have to live with; even after you have tried to move on.
There are several things you can do; the first is to talk to someone you trust or feel comfortable with. This could be a friend; a parent or a relative. Sometimes talking about it aloud eases the pain of keeping these feelings buried.
You can also try talking to a professional; either a guidance counselor or a psychologist. They can help you talk through your fears and try to find methods to help you cope.
Lastly, although you graduated you can mention to the adminstration at your High School some of the things you experienced while you were a student. This would help to draw attention to the issue and possibly help others from going through what you did. This may not affect how your high school experience was; but it might help to know you may have helped to make someone else's experience easier.
Unforunately when bad things happens to us; it can be especially difficult to forget them. Whether it's being bullied or losing a loved one; the memories tend to stick around. What's important to realize is how strong you are for coming out the other side. That is extremely important. It shows how capable you are of handeling tough situations. This is going to help you in various parts of your life. Try not to let the past haunt you and keep you down. You have too much to look foward to in the road ahead.