Step back. Good idea.
See what his reaction is.
If it's anything less than totally 100% understanding, bin him.
Don't allow your feelings to get in thé way here.
You are not a bad parent. Really. Your instincts where your ds is concerned are bang on.
The problem is, that your boyfriend DOES sulk, when a normal bloke would completely understand, and willingly back off a bit, to make sure your family unit was all cool with everything.
You should have cancelled the sleep over when your DS plans were blown out.
For one it shows that it's not right to rub the relationship in your young DS face, also if the relationship is going to be strong enough to be long term, what's one night in the scheme of things.
I am worried that you seem so vulnerable wrt relationships atm, was your last relationship abusive? If so, your revelation that this is the first bloke you 'click' with in years is more worrying, as you'll be clicking with a familiarity, which is potentially dangerous.
Be smart here. The last thing you want is to teach your DS that women are 2 a penny, and that's what your boyfriend seems to think they are.
Make him work for it!