Come up with 3 verses and a chorus. You could arrange them however you want, but V C V C V C, is a simple song. Obviously all choruses will have the same words but the verses will all be different. Make each line have a similar number of syllables, and make each verse and chorus have a similar number of lines.

As far as lyrics think of one main line that is the focus of your song. Use that line in the chorus. It repeats so make it good. Think of all the emotions you feel when you are bullied, and think of a good metaphor for each. Don't say you feel mad or sad, or angry, use the metaphor. Here's a way to come up with a good metaphor. Let's use the emotion "anger" Then think of your five senses, and answer the questions:

Anger:
Feels like
Looks like
Smells like
Tastes like
Sounds like

Not all of them will work, but it will get your ideas going. So let's suppose you say anger feels like fire. You could have a line like: "whenever you push me I feel the touch of fire on my skin".

If you feel an emotion, don't use the name of the emotion, use your physical response. When some people are scared they sweat, some shake, some get a knot in their stomach. So don't say "whenever I see you I feel scared" say: "whenever I see you my hands start to shake".

Basically people want to know what happens to you personally, use peoples descriptions, (not names), details of where, or when. Remember, I feel scared, I feel angry, is not details. You need to put people in your place, so they can relate to your feelings.
References :
I wrote these songs:
http://www.justyoursong.com/project-d/music/Will_You_Be_My_Angel_JustYourSong.mp3
http://www.justyoursong.com/media/Warm_Embrace.mp3

Good writers are good readers. Read a lot and you will learn how to arrange words to your favor. You have the experience, that is not a problem. What you need to do is to start writing all of the time.

I also write songs. On me at all times I carry a little black book. In this book I write down my ideas. I write down anything to everything that pops into my head.

I would recommend this, take the time to read the lyrics from your favorite songs. Observe how they write. Carry something on you at all times that you can write in.

Remember this: the more you do something, the better you can get with time.
References :
my life