That's a shame Mrsc, was my husbands birthday yesterday too, we had friends come round which was nice, I couldn't eat much though.
I think its ok to start buying when you like, it won't jinx it or change anything, i know people who have lost babies at 36 weeks and at 3 weeks old as horrible as it is your going to buy stuff at some point and it won't change how you feel if you loose a baby. Its good to spread out the costs or get bargains in Jan sales. I've got some little newborn cloth nappys I brought for this baby a year ago while ttc! I don't need much as got everything new with ds so will probably just get a few extra little neutral bits, I love baby grows when they are little so will get more of those!