
Oh hon...I can't imagine the heartbreak you're going through right now. PLEASE talk to someone about this; a girlfriend, a close relative, a clergy person, or even a therapist...you will need support going through this very, very hard time.
It will likely take a long, long time to get over this. You won't forget it, but it's up to you whether to move on or not. I know this is in NO WAY as bad as what happened to you, but I'll share my story...last summer, I was seeing a man I thought something could happen with. The third week of July, he ceased all contact, and then BAM...I saw on his Facebook page that he had another woman, who was DIFFERENT than the girlfriend he had been seeing on and off for the past 8 years. Just look at it as that we both dodged a bullet...it took 6 months before the crying, anguish, and hurt disappeared, although I still think of what an *ahem* he is. Especially since he got married to his woman over the summer, and acts as though nothing ever happened when he sees me.
Remember, everyone has a different way of dealing with things, and the definition of "get over it" might differ from person to person. Do what's right for YOU, and go slowly...don't jump into dating right away (yes, I have experience with this, too...another post for another time!). And I'll say this again...
talk to someone. You might not think you need the help, but there are resources out there to help us deal with this sort of thing. Best of luck to you

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P.S.- you are NOT stupid. All of us have been duped at one time or another, and it hurts. A LOT.