I have a good suggestion for you: Rooibos (some people call it red tea). It’s a plant from Africa and they use it exactly like loose black tea, however there is no caffeine in it. It tastes delicious, and you can get it with different flavours added to it. I have one at home with dried berries and it is YUMMY. It would be very good with warm milk, too.
I think your best bet however is to go to a good tea house and ask about tea and pregnancy. In good stores they will know everything about it and I’m sure they will be happy to answer your questions.