I limited myself to a couple of cups of tea per day, no more, during pg and then kinda was in the habit by the time DD was born. So for the first six months when she was exclusively bf I stuck to decaf coffee. BUT this was so I could continue to have tea and also so that the occasional soft drink or piece of chocolate wasn't on top of too much caffeine already.

You should be careful not to have too much (see the ABA guidelines that Belinda posted) and keep an eye on your baby, but you don't have to abstain altogether.