Thinking about my ex-girlfriend is simply killing me, need some help. Seriously.

Many of you already know me.
For those who don’t, here’s a brief and simple narrative of my horrible situation: the big love of my life left me one month ago. I feel physical pain when I think about her, something like there’s someone that takes my stomach and punch it repeatedly.
The problem is I am not that type of person, and I cannot afford to behave like someone that is suffering for love-related matters. I can’t because of my job, mainly, and a little because of my principles (that are questionable, of course, but nevertheless they are the ones that I try to follow). The shock subsequent of our separation kept me behaving “normally” for the first ten days. Situation is getting worse since then, at free fall speed. I cannot hide it anymore, or said better, I have to take always greater efforts to hide it, and this is becoming quite evident. Once again, I believe many of you will just say “not to repress my feelings”, and that’s what I would do if I hadn’t to look smart, self confident and all that attributes that are highly required in my work environment so I need practical advices, something small and tangible to start with.

For my self, mainly.
I want to keep my mental sanity, my awesome job, and that bloody b***ard look in my eyes that I was so proud of, just a month ago.

Thank you very much.