I have 3 of them so know how you feel. Find something your 18 month old can do while you clean, something that will keep him or her occupied so you can get stuff done. Just have patience. you will spend most of your time going back over everything you have already done it sucks but its life. Both of your kids should take a nap s why not clean in the time span of them sleeping you can get a lot done. I wish you well it will get easier though and remember your not a failure its life and sometimes it drives you crazy.