Hi Amanda
Although unusual M/S can last for most of your pregnancy and unfortunatly there is no way of knowing how long it will last for each person.
Try taking ginger either as a drink or if you can just eat small amounts of fresh ginger.
You can also buy ginger beer from the supermarket but jut be aware of the sugar content.
Anothr option would to make your own ginger tea.

Hope this helps

Aan (Midwife)