Anger Issues

I have been told by a Doctor that I have 'Aggressive behaviour issues' and that i tend to respond to everything in a argumentative manner. As much as i dislike Doctor's - this is the only thing I can agree with that the Doctor has correctly diagnosed.
I haven't always been this way, I have always been submissive, mellow and easy going.
Over the last couple of years, my Anger levels have risen - which at first, I put down to a rise in Confidence and knowledge, but now I feel the Anger.
All of my life, I have never got anywhere by being submissive and just accepting everything without questioning anything, because confidence was a huge issue for me, as was shame and fear.
I still have the fear - but the shame is long gone, so now I am left with Anger.
Anger is Soul destroying.
Nothing keeps the Anger at bay - venting/complaining doesn't work for me and only frustrates the people around me (Which is something I loathe doing!).
I have so much to be Angry about - but that is just excuses, isn't it?
I am not physically violent, but the tone in my voice has changed - to an aggressive manner, I can feel it, everything I say comes out in an aggressive way - and I hate it, I can control it, but not to the extent i would like to.
I have never really had counselling for anything - I saw a psychiatrist when I was 9 for being bullied at school and I saw a Child & Adolescent team when I was 17 for some other issues, but I have never truly opened up about my problems - Trust is another major problem - the things I should have talked about, I never could.
The Anger and trust issues have built up over the last 16 years, and sometimes I feel like I could hit someone - and I have never hit anyone in my life!
So the next book I will read will be about Anger Management, and I have finally decided to take up Running to see if I can release some of my pent up feelings. My preference is to deal with everything myself, It will probably be my downfall one day, but how can I burden someone else with my problems?