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LW: A person who loved you would not put you, and your child, through this.
If your boyfriend really considered you, and your child, as life partners - this would be a big discussion from the very beginning. He would have sat you down, and the both of you would have debated all of the outcomes. That's what COUPLES do. They talk, argue, debate, compromise, then come to an agreement. It's a "we're in this together" thing.
That's what people who love each other DO. They think of the future - THEIR future - and discuss how to handle it.
One does not go off on a job interview with a, "Oh, I'm doing this - I'll be back on Thursday." attitude. That is - at the very least - selfish, if not heartless. The fact that you have a child old enough to really feel the effects of a move, and that he doesn't seem to respect that - it's a bad sign. It's a REALLY bad sign. It shows a lack of empathy, and of 'parenting' material.
It may hurt like hell, but you may really need to move on and carry on without him. He's already left (in his mind). You have to take care of you and yours.
Buck up, take a deep breath, and realize that you deserve more than this.