I am a girl. I have a fiancee now, but back when I was in highschool, I masturbated every single day. I did not and I do not consider it an addiction.
I think your problem is that you don't masturbate enough in private time, so you get the urge to do it in public places. You have also made it your boredom activity; this is also bad because as you said, boredom can occur anywhere!!
You need to find another activity to do when you are bored. I think that will solve your issue of wanting to masturbate when you get bored in public places. I tend to zone out myself, and have random adventures or conversations in my head; but I have a strong imagination.
Whoever said that masturbating once a week is considered an addiction is stupid. WHoever said that masturbating once a day is an addiction is stupid. Hell, masturbating 3-5 times a day isn't an addiction, as long as it doesn't interfere with daily life!
SO, get something for your hands to do when you're bored! Get a stress ball and keep it in your pocket. Learn oragami, or knitting XD There are a lot of things you can do to keep your hands entertained.
You do not have an addiction.