I have a fried whose mum had awful morning sickness with all of her kids and now my friend has it. Its called hyper something so a medical term for it. It can become more serious if not looked after. My friend was very sick and ended up not working for the last 4 months of her pregnancy. From what I could gather from her she was expecting it because her mum had it. Not sure though if its destined to be hereditary though.
Hopefully you don't get it that bad!!!