you poor thing have you thought of putting lily in to childcare for 1 day a week while your DH is away, is there mothers groups around your area or even a young mums group, i go to one and i love it, they are a great group of girls.
i have a 20month age gap and i must be lucky as both are pretty good, we have our moments when madison wants all of my attension when charlotte wants a feed, but we get through it.
i would take charlie to the doc's to see why he is screaming the way he is, or go to your local health centre. Good luck.