I so feel for you 1more time.
My situation was very different to yours as we had a fatal diagnosis (totally different to yours) at 15 weeks with one of our twins. I'm now 36 wks pregnant and the poorly twin passed away 4 weeks ago. I've just woken up from a horrible dream about my 9 year old which I know has to do with all of this...
The waiting to see a specialist is horrendous and I desperately trawled the internet for information and diagnosed my baby with all sorts of things which he never had.
It's made more awful by the fact that you should be able to relax and enjoy your pregnancy and a part of you also grieves for this. I also understand the concern about being upset/stressed during your pregnancy, with my first baby my husband was undergoing cancer treatment and given a 50/50 chance of survival, I spent most of the pregnancy sobbing and having panic attacks - she is now the most amazing, chilled out, bright little girl you could ever meet so I'm not worried about the stress levels this pregnancy.
It's still very early days for you. Often fetal medical units will find a misdiagnosis from local hospitals - we were diagnosed 3 different times by three different people. We were also told our healthy twin might have microcephaly until the next scan showed that she was perfectly on the 50% centile.
Once you get to see the specialists you will be in the very best hands - often in between appointments I felt out of control and spiralling. As soon as I saw them, they were able to offer me a plan which helps you feel more in control. My best nights sleep are always after seeing a consultant.
Try to keep hope where you can. Rest when you can especially if you're not sleeping at night. Get signed off from work if it helps. Take each day as it comes - every day your baby is growing stronger inside you. Take lists of questions for the specialists and write down the answers. Keep talking to your partner, friends and family to make it feel less 'strange'. Know that you are in good company, others are in the same position as you, others have made it through this hard time, you are strong enough to do all of this.
Sending you love and strength and will be thinking of you on Thursday.