I know it's so hard to watch your child get sick with anything, but especially when they are small. Coughs can be scary, especially.
My daughter always throws up when she has a bad cough. It's actually the only way she gets the mucus out of her. She has a pretty sensitive stomach. It's almost a relief to me when she throws up, because I know she's turned the corner and is going to get better, as she's clearing the mucus.
I know she hasn't had whooping cough, because my son had it, and I know what it sounds like, and what it's like. Plus I had it, despite have five different shots of DTP in my life.
My son did catch his case of it in August, when he was about 18 months old and he had it till mid October. I caught mine in February and had it until the end of April. It was around for about 12 weeks total, with the worst of it the first two weeks, and then the cough just kind of hung on for about nine weeks after that.
Although the 'worst' wasn't that bad for ds. My son coughed a lot but he didn't have a whoop, and he never threw up. Nor did he have a noticeable fever. He played and did all his usual things. The cough was usually only rough at night.
I, on the other hand coughed so hard I'd be either doubled over or on the floor, and I gagged up crap every time. For months afteward every time there was an irritant around me, especially cigarette smoke, I would start to hack. Ds had a much easier time of it.
Vitamin C and echinachea really worked on ds. I took a lot of vitamin C and zinc, when I had it.
When/if the kids do catch something that there is a vax for, be gentle with yourself. The vaxed diseases are still around, despite the shots. Vaxed kids get diseases they are vaxed for just like unvaxed kids do. You are not a bad mother.
Wishing your ds health and healing...