joyful I am so sorry you are so and I would second all of the above - particularly 'one day at a time' - its the only way to get through, to be really thankful for each successful day, and each successive stage you get to - even tho its so scary leading up to each visit/appointment/procedure. You know yourself best and if you think counselling would help you then give it a go a talking through your fears can be a good way of feeling you have some control over them.
I lost mine at 8 weeks discovered at 12 week scan so I was not as far on as you and 18 weeks was obviously heartbreaking for you. But it does mean you get scared of every stage up to and beyond this date, as you think they are gonna tell you something awful again. It is hellish, and scary, and lonely, and the worst thing I think is that its out of your hands.
Try to hold onto the 1% thing that cece points out, too - and don't feel wierd about not telling your dh details yet, I and many others have done exactly the same for reasons of protecting ourselves and them.
Some people in RL have been really impatient with me re my negativity so I just avoid them - what we need is support and acceptance of how we are feeling as we go thru this. So chose your friends in RL carefully, and keep on using us cos that's what here is all about.
I can honestly, genuinely say that this thread and the people on it have been a really important - in fact crucial - part of my life for the last 5 months or so as I have crawled hrough the weeks of this pregnancy (bugger I am blubbing now and can't see to type)as everyone is so supportive and so nice. So stick with us...!!
Got to go compose myself now.