There’s no real proof as to what causes morning sickness, although it’s most likely attributable to the increased hormone levels you have when you are pregnant. It’s also not a given that you will experience morning sickness. Some women don’t get it at all, others only for the first trimester, some throughout their pregnancies, and some with one pregnancy, but not the one before or after.
Drinking water and eating smaller, blander meals should help, but if you find that you are throwing up, or can’t face food or water at all, you need to refer to your doctor.
There are complications, such as hyperemesis gravidarum, which is a condition which is characterised by severe nausea and vomiting which results in you eating too little to sustain yourself, or your baby.
If yours is just ordinary morning sickness, however, try your best to tough it out and remember there's a good chance the symptoms will disappear by the time you are in your second trimester.