D.R.
I am a mother of ten year old twins and at the time of their birth I was also the mother of a 5 year old. i understand totally how you feel. I can say i did not get my first good night sleep until the twins were about a year and a half years old. One suggestion is to find a trusted, experienced family member or friend who cold come and sit with the twins while you take a nap as often as you can. Most doctors will say sleep when they sleep but that only works when they both sleep at the same time.