It's hard isn't it, when you're expierencing low blood pressure. On a good day, my bp will be 90/60, in pregnancy, it's a lot lower than that.
It's hard when you've got morning sickness (I had it 24/7 with DD1, right up until I delivered her), but it is very important to try and eat whenever possible. Try and eat small meals reguarly, rather than 3 large meals.