I used to be the queen of stress, believe me, worrying and stressing does absolutely nothing good for you, and it certainly doesn't change any situation.
I'm sorry for the stress you're having. I believe the doctors are doing their job in telling you what you need to know and understand, they're not hiding anything from you which is good, I always want and expect that from my doctors. You shouldn't get upset by what they tell you, this is what they're seeing, it is what it is.
You may be in a high risk pregnancy, but that doesn't necessarily mean anything will be wrong with your baby. My sister and a good friend of mine were both in high risk pregnancies, my friend's child was expected to be born with Down's Syndrome, but he wasn't. Both delivered by c-section for their babies safety, and all went well, both boys are healthy 10 year olds. Tests can be wrong, all the signs of something may be there, the doctors need to alert you and take action, you saw that for yourself when nothing was wrong after they said your Folic Acid was high and the baby was at high risk for Spinal Bifida.
The information can't stress you out if you don't allow it to. YOU have to deal with it, you choose how to. And you are so right that the stress is affecting your baby, it can raise his blood pressure, etc., (as well as yours,) for his sake and yours you need to calm down.
Take a notebook with you to your visits and when news is presented ask exactly what the situation they're telling you about is called and write it down so you and your husband can research it online. Ask what this could mean to your baby and write it down. Ask what steps can be taken IF this is found to actually be happening to your baby and write them down. Use the information as a learning tool rather than allowing it to scare you and falling apart.
Is it possible to take someone with you to your visits, someone to encourage and reassure you, to be there for support? If not your husband, a relative or close friend? The reason being you will have many more appointments from here on out, you don't have the option to simply say you "can't take these kinds of visits anymore." It would help to have someone with you to buffer any news you receive.
In this day and age with all the medical breakthroughs out there trust your doctors to do what's best for your child. Their job is to deliver healthy babies, and in the process they need to keep you informed. Don't fear anything you hear, ask the questions you have.
God bless you and your baby, relax, get rest ~ {{hugs}}