It's good that you're seeing your GP but I am quite sure that if you had it as a child, it's a much, much smaller risk. I was in a similar situation and was told it wasn't considered a problem if you'd already had it. Obviously, there is the risk of shingles but this is very small.
To reassure yourself, see patient.co.uk This website is used by GPs and has very sensible, NHS approved advice.
There is a limited risk as you should have immunity.
There is no risk at all of shingles. Shingles is an autoimmune thing and you can't catch it from chickenpox, it's the other way around. And if you do develop shingles when pg then the only risk is that your chances of developing complications are slightly higher.
I'm sure your gp will offer plenty of reassurance.
I got CP when I was 28 weeks pregnant with my DS. Doc said only risk is early pregnancy and very late or when in labour/giving birth. But if you've already had it then you should be immune and won't get it again. I hadn't had it so had to go through the horrid spotty/itching thing -my poor bump was covered!
So don't worry, you and baby should be completely fine.