The 'job' of parenting

I often compare parenting to an occupation since I quit my job and am now a "full" time mommy. I have told many people that this job of being a mommy is much harder than my office job. There are some days I wish I was sitting at my desk updating spreadsheets and spending my lunch in solitude. Most of my lunches are now spent with kids constantly asking for something while I stand at the counter finishing off the crusts of pb&j sandwiches or slurping down a bowl of ramen noodles as fast as I can so I can help someone get a drink or wipe up a spill all while the noise level continues at a steadily loud volume of chatter or just repeating noise (right now they are chanting the words 'chiwawi' while Addy is upstairs yelling something at me that is unrecognizable to my vocabulary). I almost always felt confident in my abilities at my former job and received consistent positive feedback, pats on the back, and gratitude from those I was working under or serving so I knew I was doing things right. At this time in my life I am feeling less than adequate to do this job and am wondering why God 'hired' me for this position in the first place and why he keeps giving us more children. I am sure it's a combination of things going on in my life at this time because I don't always feel this way but it seems overwhelming and suffocating right now to have this responsibility. Being pregnant, the kids being on summer break (so no break for me), and having all had the flu over the last week, and Addison's age I am sure all play a role in my current emotions. I trust that God knows me better than I know myself and wouldn't entrust me with my children if he didn't think I was capable of handling it but I just wish I could 'feel' that right now. This pregnancy, more than any of the others, has really taken it's tole on my emotional stability. I am sure that it will pass after the baby is born but right now it feels like I will be in this fog forever. Even though I feel that this job is much harder than any other I have had I do feel that the rewards are much higher. I just need to remind myself of that in the midst of sibling rivalry, tantrums, sleepless nights, interrupted conversations, noisy meals, spills, messy rooms, seemingly never ending hunger cries, bumps and bruises, and bedtime excuses. Have you ever experienced this and if so what are some things you have done that have helped get through it? Some days I feel like my kids are literally driving me insane so I could definitely use some help from you other moms who know what it's like. I feel guilty because I want to enjoy them while they are out of school and had a vision of how great the time would be together but instead, most of the time I find myself just wanting to get away from them! What the heck is wrong with me?