I can understand your fear too, I am in a similar situation. I am almost 14 weeks pregnant with no2 and absolutely terrified of getting pre-e again. My daughter is 2 and relies on me heavily.
Like the ladies have said above, it is completely out of our control. All we can do are the things that ARE in our power...eat right, stay away from things that are not recommended during pregnancy, and try to relax, go with the flow. Im assuming, like many of us, you will classed as high risk this time and therefore receive efficient care throughout your pregnancy. If you feel something isn't right at any point, push to talk to a consultant or midwife. They are there to help.
Being relaxed and positive is key. What will be will be, and you will handle what comes along. Have you got a good support network around you?
And we're always here to chat too
~ Daughter born @36 weeks due to sudden severe pre-eclampsia, weighing 4lb 1/2oz. Now a happy and healthy 2 year old
~ Expecting baby No 2 and praying for a smooth pregnancy and birth