Hello CWWM,
I really feel for you. I had severe morning sickness, known as hyperemesis, which lasted until I was about 18 weeks. Just when I thought it was all over, I had another random bout of nausea and vomiting at 26 weeks, and again at 28.
My doctor told me that it is possible to get 'pockets of sickness', as he described it, all the way through the pregnancy. Not only is every woman different in the way that they respond to pregnancy hormones, but even different pregnancies for the same woman can be experienced differently.
The doctor said lots of other factors come into play for each different pregnancy, such as how much stress you are under, how tired/run down you might have been when you became pregnant, your current diet (that is, if you are able to manage food at all!), how much support you have from others, how much rest you are able to take, how old you are, the gender of the baby...
The nasty bout of vomiting I had at 28 weeks followed a bout of flu and a chest infection, so I was no doubt weakened by that as well.
You are not alone with your random recurrence of sickness - it does happen, but it can subside again as quickly as it arrived. Take each day as it comes, and do ask your doc for support/advice/anti-puking drugs as necessary. Try to get as much support, rest/sleep, and fresh clean water as you can - it may all help.
Big - hope you feel better soon!