Temper Temper

I have a terrible temper.  This is something I've known since I was in high school and have gotten into my fair amount of trouble and principal's office visits because of my temper.  Because I am extremely cognizant of this fact, I make a concerted effort to keep my temper under control.  So much so, that sometimes, when I'm angry, and I cover it ... it still comes across to the other party as me being angry or having an attitude. 
 
Some persons theorize that this is as a result of all this anger I have built up because of supression and as such, I really have no control over my display of anger.  Could this be so?  I mean, even when I am not angry at all, it comes across that way.  Maybe I need therapy cause this sounds like a Dr. Jeckyll & Ms. Hyde type of thing.
 
For a more peaceful life, however, I am again making the effort to keep my anger to a minimum and manage my temper .... it could be detrimental if I don't.