Struggling, angry and lost.

Hi IM's. I'm really struggling at the moment. I'm a stay at home mum to 3 kids under 7 with another on the way. I should be excited but I'm not. I'm angry, starting to feel depressed and starting to feel very, very resentful. Sometimes I hear the most vile things and horrible tone come from my mouth. It's obviously more about the way I'm feeling inside as opposed to the way I actually feel about them. I love my kids to death. There is no doubt, but geez! I feel I'm on a very slippery slope to nowhere good. My kids hardly do what they are told, they are constantly fighting and hitting each other, they refuse to help with household chores, the list goes on. For the most part they are good kids but these things seem to be constantly pissing me off. Just getting them to clean their rooms takes 3 days of screaming to get it done. My husband works long hours and has chronic fatigue so a lot of the time he falls asleep before the kids do. I feel like I'm doing it alone. This afternoon he went fishing after work. I felt myself getting angrier by the minute (not something I'd usually do over fishing). But where is my time out? Unless it involves a drs appt it doesn't happen. Where is my nap? I'm in my third trimester and anemic! I feel like I'm the forgotten one around here and just the slave. My youngest child has separation anxiety so needs to be by my side on a constant basis and always wants to be carried. I just want to shit in peace some days! I don't even know what I'm asking right now or what I hope to achieve by writing this but I just don't know what to do anymore! I feel lost and angry! I want to be a good mum to my kids, full of love and happiness but don't know where to find that person anymore.