Juliette - this is the first time Dutchie has stayed at yours?
Every time you've seen him it's been at his place, no children around (?), just basically a relaxing holiday with lots of sex and new romance. This is the first time (if I'm right) that he's been on your turf, in your territory, and you're dealing with day to day issues as well as him.
I'd say apologise to Dutchie and explain that it just takes some time getting used to, you're accustomed to this being your place and you're trying to fit two separate parts of your life together and it takes some time.
you're not being a complete bitch, your DS is a grumpy teenager and he's getting used to new stuff too - Dutchie, leaving home, loads of uncertainty in his life.
It's going to be difficult for you reconciling your romantic and day to day home life at the moment.